2001 Opposition
BAA Mars Section Circular 2001 December General The last Section Circulars were issued during the 1999 apparition. Just this one Circular is being issued for 2001, because Mars has not been well-placed for observation from the UK for the majority of 2001. It is understandable that many found that the planet was simply too low to observe properly at opposition from the UK, which was a great pity due to the large disk diameter at opposition, and to the exceptional planet- encircling dust storm which developed on June 26 and lasted until last month. At the moment Mars is relatively high and free from dust, yet almost nothing is being done in the UK apart from my own work. Back to your 'scopes, please! Observers The following contributed work in 2001, the majority from outside the UK: M.Adachi, G.Adamoli, D.Bates, S.Beaumont, N.Biver, S.Buda, T.Cave, A.Cidadao, E.Colombo, E.Crandall, B.Curcic, P.Devadas, T.Dobbins, K.De Groff, M.Di Sciullo, S.Ebisawa, C.Ebdon, N.Falsarella, M.Frassati, M.Gaskell, E.Grafton, W.Haas, T.Haymes, A.Heath, M.Hendrie, C.Hernandez, T.Ikemura, M.Justice, T.Leong, F.Melillo, C.Meredith, M.Minami, D.Moore, D.Niechoy, B.Pace, P.Parish, D.Parker, T.Parker, D.Peach, C.Proctor, T.Richards, R.Schmude, W.Sheehan, I.Stellas, G.Teichert, D.Troiani, A.Valimberti, A.Gonzalo Vargas and the writer. Thanks to all. Review of the 2000-2001 Session This was published by the Director in the BAA Journal for 2001 October. As noted therein, there was Mars news in BAA Circulars 777 and 779. It is assumed that all UK members subscribe to the BAA Circulars. This is where brief news of the great dust storm of 2001 was published. There was also a good deal about how to observe, and an early Interim Report, in the Journal for 2001 June. The Great Dust Storm of 2001 Origins Before opposition MGS imaged local dust storms, and one example in Hellas is illustrated in Astron. & Geophys., 2001 August , page 26. The image is dated April 8. There is further MGS evidence of local dust activity in Hellas in mid-June. By late June ground-based observers also detected local activity in Hellas. On the 24th, atmospheric dust was confined within the N. part of the basin, but on the 26th a long, bright, twisting ribbon of dust had extended into Ausonia, marking the emergence of an important event at Ls = 185 deg., right at the start of southern spring. The HST imaged Mars the same day but this activity was beyond the evening limb. Only the slightly dusty nature of Hellas could be seen on the latter image. But MGS temperature data (using the thermal emission spectrometer) show a warming beginning in Hellas on the 24th. The event developed quickly and dust expanded from Hesperia (long. 270 deg.) and Hellas (long. 300 deg.). Leong's image of the 27th shows additional dust in Libya with diffuse dust starting to mask the Syrtis Major and points east. Rapid expansion of the event occurred chiefly to the E. and NE, and additional activity occurred over Elysium. Within a few days the OAA were calling it a 'global' storm, but this is to misuse the agreed classification system. The dust covered much of one hemisphere, true, but in longitudinal extent it was still only a large regional event. Over the next few days Syrtis Major was effaced. So far, this was not much different from the course of many past regional storms such as 1988 June. The Director published several letters in the Communications in Mars Observations of the O(riental) A(stronomical) A(ssociation) (Japan): (no. 247, 2001 July 10) These give some historical perspective. Development On the night of July 3/4 a significant development began: a new bright dust core appeared in Daedalia in the images of Valimberti. This new storm expanded rapidly, and its incidence showed that a global forcing condition was operating despite the very early seasonal date. Over the next few days Parker and others imaged the new event's expansion primarily to the east over Solis Lacus, Valles Marineris and Mare Erythraeum (etc). Many small new bright clouds appeared around the region. The storm front crossed Noachis to link with the Hellas regional event, and the latter event had by then expanded east to meet the new event around the longitude of Thaumasia/ Mare Sirenum. By July 11 (storm day 16) the planet was encircled by dust and contrast was low everywhere. Albedo features rapidly faded from view. A pair of HST images for June 26 and September 4 published in Sky & Telesc., 2002 January, give a graphic representation of the extent of the dust. By mid-July the colour of the planet was more yellow than orange and even to the naked eye the colour was noticeably different. The dust veil extended down to a latitude of about 40 deg. north, so that the north polar hood was not veiled. The NPH became less active in August, though this could be due to the southward movement of the subsolar point. The dust had a significant warming effect upon the martian atmosphere, to the extent of 40 K or more between latitude 20 N up to the S. pole, as measured by MGS from orbit. All evidence of white cloud activity was suspended for months. Indeed, even the limb brightening was less sharp and less marked during the storm. Viewed from the Earth it was hard to see what was happening in the far south. The SPC was tilted away from the Earth and the cap, though large, was foreshortened. It appears that dust did not cover the SPC (see the aforementioned HST image for September 4) but nevertheless did extend to rather high southern latitudes. During July the only specific bright clouds were over Hellas and also over Daedalia. Several observers reported renewed activity over Daedalia, and this source remained active for some time. In August and September many observers sketched or imaged Olympus Mons as a dusky spot, showing that the storm could not have been much higher than its summit caldera. As Minami points out, the spot represents the caldera making a hole in the surrounding swirling yellow clouds rather than an albedo feature as such. Sure enough, as the dust settled, the caldera became indistinguishable. Clearance These notes are intended as preliminary only, and do not constitute a full report. From late August onwards a gradual clearing was underway, but it was very slow, and throughout September the ground markings remained hard to see well. By October the general albedo features could be easily recognised, but contrast was not back to normal until mid or late November. Signs of atmospheric dust were even then still detectable: some dust hung over Edom crater and a patch of dust hung over Argyre, whilst Hellas was still bright and yellow. In early December McKim and others still saw N. Hellas to be bright in yellow and red light, but there were no other bright dust clouds. By then all the features were sharp and well-defined, even if some were apparently not as dark as in the pre-storm period, and furthermore the SPC was again well contrasted as the southward tilt of the axis increased, though by then greatly shrunken. The storm had lasted a long time, but not quite as long as the truly global event of 1971. Historical context For a NASA press conference on October 11 at which HST and MGS data upon the great storm were to be presented, Jim Bell (who kindly set up the Mars Section web pages when he was the pro-am Marswatch coordinator) asked for the writer's views about the '2001A' storm. Here is what I emailed in reply: "I think the most important point about the present storm (2001A) is that it was seasonally the earliest ever recorded amongst all the past encircling events. It was also one of the most enduring storms, and optically one of the most dense........... It also may mark the return to the dusty climatic period that was witnessed throughout nearly the whole of the 1970s and into the early 1980s. My historical work clearly established the fact that encircling storms were witnessed every martian year from 1971 to 1977. It showed that 1975 contained a planet encircling storm, a fact not widely appreciated, and this year together with 1971 and 1973, when coupled with the Viking data up to late 1977 show the emergence of a great storm every year on Mars (with two in '77). This epoch was unprecedented and Viking's cameras recorded an atypical Mars: a fact well worth reiterating. During this epoch both Hellas and Thaumasia/Daedalia dominated the scene as emergence sites, indeed they remain the only such sites for the emergence of encircling storms. "The 2001A event is important in possibly marking a return to dusty climatic conditions: but by definition we shall not know for at least two or three more martian years. "The development of the 2001 event was similar to many past great storms........ It began with what appeared to be a large regional event originating in the Hellas longitude. In this respect the storm was not seasonally especially early. Historically, regional storms from Hellas had begun at even lower Ls (see the tables in the BAA Memoir). One more discovery from my book [Mem. Brit. Astron. Assoc., 44 (1999)]. I divided up the last century and a half into epochs: 1866-97; 1898-1929; 1930-61; 1962- 93. I wrote on page 144 in connection with the Hellas emergence site: "In the last three epochs, the R(egional) type storms have begun progressively earlier in the season." It seems that the 2001A event's timing has also been unusually early. Is there a simple physical mechanism for this phenomenon, associated with the gradual net accumulation of dust grains at a site? "Event 2001A became planet-encircling when a secondary source of dust emergence commenced in Daedalia about July 4, and together with the initial dust outbreak carried dust around the globe. All the great storms have become encircling in this way when a secondary source supported the initial outbreak elsewhere: for example, the 1973 event began in Daedalia/Claritas, but it had secondary outbreaks over Hellas and Meridiani Sinus. "There is a possibility that the retreat of the SPC began early in 2001: I have made no measures yet, and it is just a possibility. In 1986, the SP hood cleared at Ls 180, but in 2001 the hood was already cleared by then. "The 2001A storm showed a more vigorous expansion to the north than some of the most recent encircling events. Thus the area of Syrtis Major was blotted out from view quickly. As to its duration, it is still in evidence, though clearly dying out now. Thus its duration will be greater than 15 weeks, or 105 days. It will probably last no more than another few weeks. The durations of the planet-encircling storms of the 1970s-80s dusty epoch were (my data): 1971 161 days; 1973 91 days; 1975 100 days; 1977A 60 days; 1977B 158 days; 1982 110 days. "For visual observers 2001A was probably the most opaque storm since 1971, although the 1971 storm was more global in its dust coverage. Of course, the 1977 and 1982 Viking data were a little incomplete." The MGS data for the 2001A event have been written up in the paper Thermal emission spectrometer observations of martian planet-encircling dust storm 2001A by M.D. Smith, B.J. Conrath, J.C. Pearl, and P.R. Christensen and it was recently accepted for publication in the journal Icarus. Changes upon the martian surface As is usual with big dust storms, some changes upon the martian surface were apparent. Prior to the storm, the markings were much as they had been in 1999. Nepenthes was invisible, Cerberus and Trivium Charontis nearly so; Nodus Alcyonius, the Amenthes darkening and Solis Lacus were all prominent. After the storm, Parker remarked that Syrtis Major appeared thinner, and the writer found it more tapering to the north in his recent work; at the same time, Deltoton Sinus had become more visible. And there was a new dark marking just W. of Solis Lacus, greatly resembling the old 'Phasis' canal shown on the maps of G.V.Schiaparelli and N.E.Green from 1877. This was imaged from early September onwards, when Solis Lacus itself was still mostly hidden by bright dust clouds. (This feature was also observed during the mid-1980s through the early 1990s.) Solis Lacus itself was smaller after the storm, and the feature known as Nectar, connecting Solis Lacus to Mare Erythraeum was greatly faded. The rest of the apparition Mars is still very much observable, upon the meridian early in the evening, though he is now only some 7 arcsec across. Work should continue into 2002 as far as possible until Mars is lost in the evening twilight. There may even be further dust activity, given that we are still within the martian southern hemisphere summer season, and accurate recording of the size and shape of the SPC is important for comparison with the historical records. The Director is enjoying good views at present, despite the tiny diameter. The markings are clearly defined upon the strongly phased disk, and the planet is crowned by a small SPC summer remnant. Publicity for the Mars Section The Director gave a talk to the Cambridge University Astronomical Society on November 7th. Affiliated societies such as CUAS have in the past produced useful reports for the BAA planetary (and other) Sections, and the Director would appeal to local society coordinators to do all they can to increase the input of observational data. The very next day, I was in Oxford, presenting a colloquium on the theme of dust storms to the Department of Physics. This gave an interesting opportunity to see the computer modelling of storms being done by the Oxford team comprising John Barnett, Peter Read, Claire Newman, Stephen Lewis and others. It was gratifying to know how helpful they had found the Mars Section Memoir (see below) to be. At the Winchester Weekend meeting in 2002 March the Director will present an illustrated talk entitled 'Perihelic Oppositions of Mars', and this will include a full review of the present apparition. Mars Section Memoir on Telescopic Martian Dust Storms Copies of this book by the writer are still available for sale from Burlington House. Don't delay too long as all copies will ultimately be sold out. This is the only book that exists devoted to the study of dust storms! Telescopic maps These can best be found in the above Memoir. The Section continues to recommend the general map of Shiro Ebisawa, with his nomenclature. A simpler general chart is the IAU map by de Mottoni (1957), but it does not always have sufficiently detailed nomenclature. Another good source is John Murray's albedo map given in the latest edition of Norton's Star Atlas. All these maps inevitably become slightly dated as albedo features change, but all represent an 'average' Mars. Section Programme For non-members of the BAA who read this, our programme and observing tips are featured in the BAA Observing Guide (formerly known as Nature, Aims and Methods), which can be purchased from BAA headquarters. A new edition is being prepared by the writer for 2002. Historical note: Landscape Painting, Queen Victoria and the BAA Mars Section What do the above have in common? The answer is a man who was called Nathaniel Green. N.E.Green (1823 - 1899) was a famous English amateur astronomer of the late Victorian period. A landscape painter who exhibited at the Royal Academy in London, Green once included Queen Victoria among his pupils. He was one of the founder members of the BAA in 1890, was President 1896-98 and for some years directed its Saturn Section. By then, Green was already famous for his drawings of the planets, having previously published them in the Astronomical Register and in the Memoirs of the Royal Astronomical Society. He is best known for his 'soft-pencil' views of Mars from the island of Madeira in 1877, at a time when Schiaparelli was covering the planet with fine canali. In 1894 the BAA Mars Section Director B.E.Cammell produced a manuscript report which was too long for the Council to publish. Green was prevailed upon to edit the Memoir down to a more acceptable length, and this he did. When he died, Green left his 18-inch mirror to the Association. This was later used at Headley observatory for many years by the Rev.T.E.R.Phillips, mostly for Jupiter and Mars. In recent years it was at Conder Brow with Denis Buczynski. For many years I have casually looked for Green's non-astronomical works without success. But a few weeks ago in an antiquarian bookshop in Stamford I came across a lovely copy of a book Green wrote in about 1880 entitled Hints on Sketching from Nature. I knew that Green wrote more than one book upon the subject, but had never seen any examples. This lovely little work about watercolour landscape painting was published by Rowney & Co., the firm who produce all sorts of artists'9 materials, and was intended to encourage art students new to the craft. Indeed, Green had Rowney & Co. print for his own (and BAA members'9) use cards bearing a series of 2-inch diameter planetary drawing blanks, each disk being ochre-tinted and set upon a black background. You can draw on these disks in pencil or pastel, and then scrape away the ochre tint to give the highlights. I have a stock of these cards in the Mars Section archives, and Richard Baum and I once tried them out. The little art book gives beautiful coloured lithographic reproductions of some of Green's works. Oh, to own an original! Flowers for Tycho My favourite tram ride in Prague is to take tram no. 22 from Malostranska metro station, up the hill to the ancient streets above Prague castle. This route offers lovely views over the city as the tram attacks the steep hill and sharp corners. Then, if you get out at the right stop, you face a large statue of Tycho Brahe and Johannes Kepler. Just behind is the modern Jan Kepler Gymnasium, Prague's top school, and inside there are foundations of a house in which Kepler once lived. Tycho is buried in the Tyn Church in the Old Town Square, a stone's throw from the famous astronomical clock of the Old Town Hall. I have visited the tomb several times and recently I went to see the statue again to mark the 400th anniversary of his death. Czech astronomers had laid flowers there in Tycho's memory. And finally...... Thanks are due to all those who contributed data in 2001. Please be patient with the Director as he slowly prepares the backlog of formal reports for the Journal on the apparitions of 1995, 1997, 1999 and 2001. The 2003 apparition will be better than 2001, of course, and we hope to see the Beagle 2 lander arrive in Isidis Planitia to look for evidence of past water in 2003 December or 2004 January..... I look forward to making an early start to that great perihelic apparition! Richard McKim, Director 2001 December 12th; Ls = 289Back to Date Menu
July 16 - August 31, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 8
General
This Circular summarises the period 1999 July 16 (Ls = 171 deg, D = 10.3
arcsec, decl. = -14 deg.) to August 31 (Ls = 197 deg, D = 7.9 arcsec, decl.
= -21 deg.). Mars remained an increasingly difficult evening object, and the
last UK observation received is that by the Director on August 10, observing
>from Truro on the eve of the total solar eclipse. The planet has been easier
to view from the USA, Italy and Japan, etc. Since the last Circular I have
received observations from Parker, Foulkes, Crandall, Di Sciullo, Melillo,
Wasiuta, Topping, Teichert, Niechoy, Meredith, Johnstone, Hendrie, Heath,
Haas, Grego, Colombo, Adamoli and Frassati, six of whom had not sent
observations earlier this apparition. Especially praiseworthy among the
visual observations are the series of later drawings by Haas, Frassati and
Adamoli, which continue to document the changing polar regions and white
clouds.
MGS observations 1999 June
MGS observations of dust activity in the N. polar region on June 30 were
released onto the Web on August 10, in other words since the last Circular.
The images are dated June 30, 0652h, 0850h, 1047h and 1245h UT, showing the
hemisphere of Mare Acidalium. A dust cloud curls southward from near the NPC
remnant, concealing Hyperboreus Lacus. (See Extract B from the MGS Website,
below.) The Director was not aware of this event at the time, so he could
not alert observers. But the region was on the wrong side of the planet to be
viewed from the UK at that time. Japanese observers may have viewed some
indications of the event in early July.
It will be recalled from Circular No. 6 that of the BAA observers, Cidadao
and McKim viewed dust activity in the Mare Boreum region on June 2-3, not far
>from the event of June 30. This area, adjacent to and NW of the large dark
area Mare Acidalium, has therefore produced several small dust events and
white ‘cyclonic’ clouds (see an earlier Circular) during the apparition.
Historically the region has produced other ‘cyclonic’ clouds during the 20th
Century. But what about dust storms? The large albedo and thermal inertia
contrasts between Acidalium and the neighbouring classical deserts of Tempe,
Chryse, Xanthe has occasionally led to dust initiation in the latter desert
regions, but I cannot recall dust activity starting over Mare Boreum during
the period reviewed in the Dust Storm Memoir (i.e., up to 1993). This all
goes to show that Mars can still surprise us. Past records of a yellowness
about the polar regions should therefore not be dismissed immediately as
observational error! In the Mars Memoir (see later) I have called attention
to such polar dust records, and briefly describe my results. But after the
martian polar storms in the summers of 1997 and 1999 it may be prudent to
further reexamine some historical data…….
Extracts from the MGS website
Herewith some exciting extracts from the Web. Of course, you need to see the
pictures! I picked the comments most relevant to the groundbased observer. I
have taken the liberty only of improving the spelling on the Website
(sorry!), and of adding a few of my own comments in square brackets [ ].
Extract A
"Wind Action--The Dust Devils of Amazonis Planitia
MGS MOC Release No. MOC2-171, 10 August 1999
Dust devils result from spinning vortices of air that lift dust from a
planet's surface. They look something like a miniature tornado. The dust
devils shown here were observed in mid-May 1999 in northern Amazonis Planitia
(northwest of the Olympus Mons volcano). Dust devils are common in this
region and were seen there even during the Viking orbiter missions in
1976-1980.
The first two pictures (A and B, above [see the Website! - RJM]) show a
colour composite view of the Amazonis dust devils as they appeared to the
Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red and blue wide angle
cameras; the white arrows in MOC2-171b (B, above) point to each individual
dust devil. The third picture (C, above) is a GIF "movie" (Click on the Icon)
that shows dust devil occurrences on two different dates in May 1999. The
scene in this "movie" is about 88 kilometres (55 miles) across. The fourth
picture (D, above) is a diagram that compares the typical heights of dust
devils and tornadoes on Earth with dust devils on Mars. Click on the
"cartoon" icon to see the entire diagram, including a comparison with the
heights of the tallest mountains on Earth (Himalayas) and Mars (Olympus Mons).
The heights of dust devils in MOC images can be estimated from the length of
the dark shadows that they cast. The shadows in these pictures all point
toward the northeast (toward upper right). The largest dust devil in these
pictures towers nearly 8 kilometres (5 miles) above the martian surface, and
has a lower basal plume of dust that suggests substantial surface flow of
wind and dust into the rising column. In the MOC images shown here, north is
up, and the sun's illumination is from the lower left. The 40 kilometre scale
bar also indicates a distance of about 25 miles. Additional MOC images
regarding these and other dust devils:
•"Large Martian Dust Devils Caught in the Act," July 1, 1999. •"SUV Tracks on
Mars? The 'Devil' is in the Details," July 30, 1998."
Extract B
"Late Summer Storms Over the North Polar Region
MGS MOC Release No. MOC2-172, 10 August 1999
Storm clouds have been brewing over the north polar cap of Mars since the
last week of June 1999. During the month of July, summer was ending; autumn
began at the start of August. The wide angle cameras of the Mars Global
Surveyor (MGS) Mars Orbiter Camera (MOC) have been documenting the changing
weather patterns of the red planet nearly every day since the Mapping Phase
of the mission began in March 1999. These images are showing many more
details about martian weather than had been previously recorded. Mars is a
dynamic planet, with weather systems as complex and exciting as the Earth's.
The four still-frame images (above) show the evolution of a storm system that
developed over the martian north polar region on June 30, 1999. Each picture
was taken approximately 2 hours later than the previous. The north polar ice
cap is the white feature at the centre of each frame. Clouds that appear
white consist mainly of water ice, clouds that appear orange/brown contain
dust.
This particular storm system lasted well into the next day--July 1, 1999. A
total of 23 red and 23 blue camera images were used to create a time-lapsed
"movie" that displays the development and evolution of this storm over the
two-day period. Of great interest are the "curling" of the clouds behind the
largest of the storms--this indicates a flow vortex that follows the storm
front that is moving toward the top/upper right of the frame--and the
correlation of white water-ice clouds with orange/brown dust clouds. High
surface winds must have raised dust and mixed it with water vapour in the
air over the summer-time polar cap to create this effect. To view the
"movie," click or download to your desktop the following 2.2 MByte MPG file.
Storms similar to those shown here were observed to continue throughout the
month of July and into August [unfortunately there are no details given on
the Website - RJM]. Over the next several months, the north polar cap will
grow dark as the region transitions through autumn and into winter. When
northern winter begins in December 1999, this region will be dark and
obscured by clouds." [This is not so: the NPH will be a permanent feature
well before 1999 December! - RJM]
Extract C [quoted in part only]
"Mars: An Active Planet
MGS MOC Releases MOC2-166 to MOC2-172, 10 August 1999
Among the goals of the Mars Surveyor program are to characterize the planet's
climate and the interaction of the atmosphere with the planet's surface. Both
the Mars Global Surveyor (MGS, presently in Mars orbit) and the Mars Climate
Orbiter (MCO, which reaches Mars in September) address these goals in part by
using cameras to observe martian weather and changes on the surface that
occur from season to season.
Mars Global Surveyor has been orbiting the Red Planet for just over 1 martian
year (687 days). Although the spacecraft only recently attained its final
design orbit after 18 months of aerobraking and other orbit phasing
activities, "snapshots" of Mars acquired during this period by the MGS Mars
Orbiter Camera (MOC)--when it has been on--and more recent views from the
present mapping orbit have captured a unique record of seasonal and
meteorological events that demonstrate that the planet is quite active and
dynamic today.
Evidence for present-day activity comes in two forms--weather, and surface
changes. Detailed weather observations include the tracking of dust devils
and the daily mapping of cloud and storm patterns. Other changes on the
planet have been seen among frost-covered sand dunes. These changes are
connected to the passage of martian seasons and the retreat of polar ice as
winter draws to a close and spring begins. As the winter ice begins to
sublime, dunes develop small dark spots that grow and eventually coalesce
until the frost disappears. Some dunes show evidence that wind and gravity
are actively moving the dune sands, as well.
The images shown below were presented at a Space Science Update briefing at
NASA Headquarters, Washington, DC, on 10 August 1999. For the corresponding
JPL Press Release, see: www.jpl.nasa.gov/news/.
1. The Mystery of the Spotted Dunes
Back to Date Menu
June 1 - July 15, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 7
General
This Circular summarises the period 1999 June 1 (Ls 147 deg, D 14.2
arcsec, decl. -10 deg.) to July 15 (Ls 171 deg, D 10.3 arcsec, decl.
-14 deg.). Mars has been an evening object, and to see him at reasonable
altitude from the UK, near the meridian, has meant picking him up against a
light blue sky. Some of the early June observations were reported already in
the last circular. Further contributions have come from B.Adcock, T.W.Leong
and M.Valimberti (CCD images), M.Adachi, D.L.Graham, D.P.Joyce, P.Lyon
(photos with 20-cm SCT), P.W.Parish, J.D.Shanklin, D.M.Troiani, and A.Van der
Jeugt. Peter Lyon managed some excellent photos from his site in Birmingham,
and I am quoting in extenso from his letter of June 21, to pass on details of
his experiments concerning film and technique. His are the only photos
received in 1999; last apparition I received photos from just two observers.
There is no denying the great aesthetic value of a nice planetary photograph,
and I hope observers will still make them, if only for the sake of historical
continuity and as a true test of skill. He prefaces his discussion with the
comment that given the pace of digital camera progress, the details may be
less useful in 2001!
Photographing Mars in 1999 by Peter Lyon
"Exposure lengths: The criteria will differ with every telescope/camera set
up, but on my portable C8 SCT I have found that in an exposure of 2 seconds
or more the initial vibration (about 0.3 seconds) due to the camera shutter
does not show up. For Mars at image scales above f/100 this usefully is the
exposure required anyway on colour slide films which are sufficiently fine
grained to record fine detail. I favour 2 second exposures to avoid
excessively precise polar alignment, which are short enough to test for
vibration on the Mon even without a special lunar drive rate.
Films: Initial tests on Agfachrome RSX 50 Professional colour slide film
simply served to confirm an exposure for Mars of 2 seconds at f/110 (from
UK), but the film although giving good colours seemed to lack contrast and
was far too coarse-grained for Martian detail. Kodachrome 25 at f/110 and 4
seconds exposure gave good contrast, fine grain and a vivid green colour (for
Mars!), so was definitely not suitable. Kodachrome 64 at f/120 and 2 seconds
exposure perhaps suffers somewhat from reciprocity failure. The grain, while
coarser than the Kodachrome 25, was reasonably acceptable but the colours are
(not surprisingly) those of 'old' Mars photos - a pinkish hue for the desert
areas and a mauve tint to the dark markings (which have reasonable contrast).
Fujichrome Velvia (50 ISO) at f/110 and 2 seconds exposure must, for theis
selection of films, be regarded as the definitive film for Mars. The colours
are recorded, with no hint of any shift in colour balance, precisely as a
pleasant orange hue for the deserts with quite neutral dark markings and the
smoothness of very fine grain completely surpasses both of the Kodachromes. I
have no doubt that this film, at this image scale, could record all detail
that the telescope can resolve, without resort to high contrast
black-and-white films. The contrast of the Fuji Velvia, although not
dramatic, is well up to the task and is quite amenable to enhancement by
slide duplication techniques."
BAA and other observations, 1999 June 1 - July 15: mostly concerning the polar
regions I have carried the observations up to July 15 in order to document the
most interesting phenomenon of the moment: the appearance of the N. polar hood.
Signs of a permanent polar hood mark the late June observations, and
occasionally before that time. In Circular No. 6 the 'polar cyclone' of HST
was described: such large white clouds are often seen as a precursor to the
formation of the hood. Two further events were witnessed by members of the
OAA in May and June.
Several observers in late June portrayed the cap as being diffuse at the
edges, and sometimes less bright than earlier on. The latest CMO (OAA) No.
220 to reach the Director describes the period June 1-15 as observed from
Japan. As late as June 14th Olympia and Rima Borealis were still visible.
During all that period the NPC was observed. On June 18 (Ls 157 deg.) under
CML 322-338 deg. the Director found the S. edge of the NPC less sharp and the
cap slightly less bright. The NPC seemed sharper on the 20th under CML
295-298 deg., but seeing was mediocre only. And on the 24th, CML 259-267
deg., there was a cap with brighter haze to its south. Bad weather then
intervened. Using Michael Hendrie's 15-cm OG on July 9 (Ls 167 deg., CML
96 deg.) the Director had an excellent view, when a definite change in the
aspect of the area was evident; the slightly less bright hood was larger and
somewhat diffuse over the N. limb. He found the hood brighter and a little
larger still on July 11 under CML 86 deg. My later observations constantly
show a hood.
Meredith's sketches suggest an increase in the size of the NPR in late June:
an overlying hood forming? Elisabeth Siegel, June 19, CML 302 deg: "It
seems to me that the NPC has grown a little bit since the beginning of June"
And Teichert on June 17-28 found the NPC faded, and blurred at the edges. The
combined work of Cidadao and Parker seems to show a polar hood present during
June 25 to July 7. In 1999 the hood has therefore appeared to cover the cap
entirely by early July. (Ls 163 deg. on July 1.) The receipt of further
data will enable these limits to be refined later. In any case, this is
typical seasonal behaviour. In 1984 the hood appeared at Ls approx. 161 deg.,
for instance, though it was not constant at all longitudes to begin with.
At the same time, throughout June and July we have had a very bright S. limb,
which exhibits still brighter patches from time to time. Especially bright
parts are those corresponding to northward incursions over Hellas, SW
Thaumasia (or Claritas) and Argyre. This entire area is foreshortened and
hard to observe well except in very good seeing. My impression is that it is
(at least from July onward) now the ground cap, showing as it does a fairly
sharp N. boundary: I have not yet tried to analyse the precise transition
from one to the other. (In the past, I have looked for the visibility of the
cap in red light, while the brighter patches within the hood have been taken
as signs of the ground cap showing through. More data please!) In 1984 the
SPC was present from about Ls 161 deg., at the same time as the NPH covered
the NPC, in fact.
No certain reports of dust activity have come to hand. No changes in the
surface features have been detectable upon the rapidly shrinking disk.
Reports of white clouds continue to be received, but I do not intend to
describe them further here, suffice to record that the ECB appear to have
finished, and cloud activity generally, except in the polar regions, seems
less prominent.
The BAA Dust Storm Memoir:status
The BAA Dust Storm Memoir is now in press, the corrected proofs having been
returned to the printers a few days ago. Watch this space! For now, here is
the Abstract of the Memoir:
The dust storms of Mars have fascinated the planetary observer since the
first observed planetwide event of 1909. To an extent predictable, but
notoriously variable in amplitude, the dust storms appear as orange, yellow,
or yellow-white clouds, best imaged in red light. Today, the majority of
telescopic events are still discovered by amateur astronomers. Apart from
colour, dust storms exhibit motion and obscure underlying albedo features.
Temporary, anomalous darkenings associated with yellow clouds arise from the
removal of the thin surface veneer of dusty material to expose darker
bedrock. Dust movement also accounts for all long-term albedo changes of the
classical martian surface markings. The present work, the result of a
wide-ranging survey of the literature since 1659 and much unpublished
archival material, identifies dust storms as early as 1704 and as late as the
1990s, but the timecourse of such phenomena has been followed effectively
only from the late 19th century.
The following account draws heavily upon the published and unpublished work
of the BAA Mars Section (1892 onwards). The records for 1922-39 and 1943-54
have been analysed for the first time, and the entire archive re-examined. A
coordinated narrative account of the dust storms observed during every
martian apparition has been produced, so attempting to collate for the first
time all the work of the diverse observers and groups. It chronicles the
dates, extent and movements of observed yellow clouds (and suspected yellow
clouds and obscurations), and provides comprehensive references to the
telescopic literature. In the latter respect, the author has tried to cite
all relevant telescopic studies conducted since 1901, the limit of
Flammarion's great two-volume work on the planet. Comprehensive narrative
accounts of many newly recognised regional storms, and of the encircling
storms of 1909, 1924, 1956, 1971, 1973 and 1975 are published here for the
first time. A contemporaneous review of the major albedo changes on the
planet has identified past dust storm sites, even where the storms themselves
were not directly observed. Many new minor events have been detected, whilst
in reviewing the extant catalogues, numerous spurious 'events' have been
shown to be records of limb or polar haze, white cloud, observational errors
or duplicate records of the same event.
The account closes with a revised dust storm catalogue, a complete location
map, and histograms and statistical analyses of the data. This new study
confirms that there are 'preferred' emergence sites which vary with time.
Hellas features largely in the statistics for the epoch 1909-1988, with the
Libya-Isidis emergence site being of major importance up to 1958/59. It is
shown that despite the less complete temporal coverage before the 1890s, the
18th and 19th centuries genuinely appear to have been deficient in major, or
encircling storms. It will be important to continue the ground-based record
for many years in order to improve our statistics of all types of yellow
clouds.
The Memoir will be published as hardcopy ONLY, and there is no intention to
make it available on the Internet.
Other recent publications
* Don Parker et al. describe the ALPO 1997 observations in Icarus, 138, 3-19
(1999).
* Ted Stryk published his observations of 1996 January, when significant dust
activity was inferred from the CO microwave data of R.T.Clancy, in J. Assoc.
Lunar Planet. Obs., 41 (2), 76-77 (1999).
* Paolo Tanga has written up the UAI's 1995 Mars work in l'Astronomia, 1999,
No. 1, pp 2-11.
Reporting data to the Section
I am always happy to receive CCD images by email. Any URGENT and important
drawing can be scanned and sent as an image file, but I do not want to
receive routine drawings by email, because the vast majority are sent to me
as hard copies, and that is the form I like to compare (and archive) them in.
I have to again write that I am spending a disproportionate amount of time
downloading files sent to me over the Internet, then decoding, analysing and
refiling them in the Section's records! Send mail to Cherry Tree Cottage, 16
Upper Main Street, Upper Benefield, Peterborough PE8 5AN, Great Britain; home
telephone 01832-205387; home email Rmckim5374@aol.com. (Do not use the former
email address for my place of work (mckim@oundle.northants.sch.uk).) Urgent
faxes can be sent to my place of work on 01832-274052.
The next Circular
The apparition is all but over for UK observers, given the low altitude and
small disk size combined. I will therefore issue just one more circular this
apparition. So let me have your July and August observations by September 15,
so that the final circular can be issued later that month. Of course, do keep
trying to observe even longer if you can, and send in your results whenever
possible.
The future reports of the BAA Mars Section
Although preliminary accounts of the 1995, 1997 and present apparitions have
been published, final reports have yet to be completed for all these years.
If anyone reading this has good data for any of these years, but has not yet
submitted it, please do so now. With the completion of the Memoir, I shall be
working on final reports on 1995, 97 and 99 during the autumn.
Good observing!
Richard McKim, Director, 1999 July 18th
Back to Date Menu
April 16 - May 31, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 6
General
This Circular summarises the period 1999 April 16 to May 31 (Ls 130 to 147
deg). The planet was at opposition on April 24 (Ls 129 deg., D 16
arcsec., lat. of centre of disk 18 deg. N, decl. -12 deg.). By May 31, D
had decreased to 14.2 arcsec., and at the time of mailing this Circular D
has fallen to just over 12 arcsec.
The UK weather has remained unhelpful on the whole: compare the number of
clear nights in 1999 with the splendid weather near opposition in 1997, when
Comet Hale-Bopp was well-placed. Personally I have managed only 40 drawings
with my 22-cm reflector. But this is the busiest time of the academic year
for me, and although I am grateful for having received a deluge of post and
email, it has not always been possible to reply at once: most of my time has
been spent in merely filing away the data to look at later! In addition to
those observers listed in Circular No. 5, I am grateful to Paul Abel, Tom
Cave, Antonio Cidadao, Maurizio Di Sciullo, Colin Ebdon, David Fisher,
Maurice Gavin, Michael Hendrie, Henk Munsterman (via Wim Cuppens), Terry
Platt (via Maurice Gavin), Elisabeth Siegel, David Storey and Myron Wasiuta
for sending me observations. Apologies to anyone I have forgotten. Michael
Hendrie's sketches (15-cm OG) are very good representations of the planet's
features, and Johan Warell made excellent use of a 16-cm apochromat.
Australian planetary coordinator Bary Adcock sent excellent CCD images by
Stefan Buda and Bratislav Curcic (25-cm Dall-Kirkham Cass.). Antonio Cidadao
(Oeiras, Portugal, 25-cm refl.) and Maurizio Di Sciullo (Coconut Creek,
Florida, USA, 25-cm refl.) have sent amazing colour CCD images, and
Maurizio's can be seen in the July issue of Sky & Telescope, page 124. Jean
Dijon's monochrome ones, secured from his observatory in France, are superb
too, but most other European images have evidently been limited by less
favourable seeing conditions.
Antonio Cidadao's images seemed so good that I asked him if he enjoyed
excellent seeing. In fact he does not, but he does have some extensive
experience in image processing, so here are his remarks which may be helpful
to others:
"I did begin to obtain CCD images in 94, but the only camera I had at that
time was not the best to get planetary photographs (a ST6, with large
pixels). Nevertheless, I did obtain some images for pictorial purposes, and
to optimize a technique that would allow me to get the best resolution I
could. You can take a look at a first version of that technique (I still use
it now) at my Geocities page
(http://www.geocities.com/CapeCanaveral/5409/planet_index.html). I later on
found out that such manual "super-resolution" approach from under-sampled
images was nearly identical to that applied by Tim Parker from the JPL to
process the Pathfinder lander camera images. Since then I have been in
contact with him. So, I must tell you that I do NOT have 'super' seeing
conditions : I wish I had. In fact I work from a 'roof-top' window
observatory that heats up considerably during the day and is surrounded by
some 3 or 4 'active' fireplace chimneys. Believe me, I can tell the
difference when people start to use them during the winter. What happens is
that I try to fight a lot to get the best possible resolution by averaging a
lot of registered frames. For instance, for each final filtered component of
my Mars images I average some 30 to 50 original images (about 15 for Jupiter
since it does rotate faster). That's a lot of processing to do but it does
seems to work..." It certainly does!
MTO-II in Icarus
Mars Telescopic Observations-II: this was the course the Director attended in
1997 in Tucson, AZ. Some papers from the proceedings have now been formally
published in Icarus, 138 (1), 1999 March. I would appreciate reprints from
any authors reading this Circular!
New global topgraphic Mars maps
John Rogers reports that some excellent coloured maps have appeared in
Science (284, 1495) in June, and have also been placed on the MGS website.
News from the HST
In a recent Marswatch electronic newsletter there was some reference to the
HST work. As has been noted previously in these Circulars, Hubble has been
taking very few images this apparition. Here is the relevant extract:
"HST Mars observations: April 27 through May 7
All of the planned Hubble Space Telescope (HST) observations of Mars for this
opposition have now been scheduled. HST will observe Mars at four central
meridian longitudes (for full global coverage) between April 27 and May 7
(hopefully the recent failure of one of the HST gyros will not hinder this!).
The exact times when HST will be observing Mars are indicated in the table
below (times are given in Greenwich Mean Time or Universal Time, which is
currently four hours ahead of U.S. Eastern Daylight Time). I am organizing
these observations, and I am *especially* interested in obtaining supporting
groundbased CCD images from amateurs and professionals during the times when
the STIS instrument (Space Telescope Imaging Spectrograph) will be observing
Mars. For the times when STIS is observing, we need high quality CCD images
especially in the blue, so that we can determine where clouds, hazes, and
fogs are most likely interfering with our spectroscopic measurements. If you
are able to observe Mars in the blue at these times, we would greatly
appreciate receiving copies of your images and their descriptions! We will be
posting the HST images onto a Web site as soon as we get them processed.
1999 HST Mars opposition observations
Visit Instrument Start Time (GMT) End Time (GMT)
----------------------------------------------------------------------------
1 WFPC2 Apr 27 1999 17:55:38 Apr 27 1999 18:51:12
2 STIS Apr 27 1999 19:32:20 Apr 27 1999 23:23:27
4 WFPC2 Apr 28 1999 00:22:25 Apr 28 1999 01:17:59
7 WFPC2 May 1 1999 13:47:34 May 1 1999 14:43:08
8 STIS May 1 1999 15:24:53 May 1 1999 19:14:14
5 WFPC2 May 6 1999 11:28:10 May 6 1999 12:22:14
6 STIS May 6 1999 13:04:18 May 6 1999 16:51:20
3 STIS May 7 1999 06:52:54 May 7 1999 10:55:14"
As BAA data cover every date during April and May, no doubt at least some of
our observations will coincide with the HST images. Members having CCD images
close to the above times are invited to send Dr Bell duplicate copies, if
they have not already done so.
Mars Global Surveyor News
MGS is very active, and plenty of new images have been posted on the WWW. The
Marswatch newsletter also contained a paragraph about the status of MGS:
"Update on the Mars Global Surveyor Antenna Glitch
On April 15 the Mars Global Surveyor spacecraft experienced an "anomaly" (a
glitch) with its main high-gain antenna. Apparently one of the hinges on the
high gain antenna got stuck, meaning that the antenna can only swing in one
direction instead of in two directions. JPL engineers are troubleshooting
the problem, and mapping has been put on hold. The plan is to continue
mapping next week because high speed communications with Earth can still work
for now even if the antenna can only move along one axis. Check out the April
23 and earlier updates for many more details:
http://mars.jpl.nasa.gov/mgs/mgs-readme.html
Also, check out some of the spectacular early mapping data at:
http://www.msss.com/mars/global_surveyor/camera/images/index.html"
BAA , HST and MGS observations April 16 to May 31
I have sometimes gone a little way into June in order to continue the
narrative.
1.1 Surface features
Fine surface details have been imaged and sketched throughout the period
under review, but as mentioned earlier, these details are closely similar to
1997, even at the resolution of the HST. Gray caught the dark patch inside
the Huygens crater, which lies in W. Iapigia. With the better resolution near
opposition some observers were able to detect the little feature Gallinaria
Silva, the 'oasis' following Solis Lacus which I use as a sort of indicator
for secular change in the region. It was inconspicuous. During the last
opposition it appeared from Parker's CCD images that part of the following
(W. areographic) side of Solis Lacus was fading a little. This fade has not
continued during the current apparition, and Solis Lacus therefore remains
unusually large and dark.
A few observers noted the apparent martian colours. Amongst them was
P.Devadas (Madras, India, 36-cm refl.) who on April 20 found M. Acidalium
grey compared with the bluish-green tint of the S. markings under CML 57
deg. This difference in apparent colour between the N. and S. markings has
been remarked upon before. On May 23 Frassati found Propontis (I) to be dark
brown. (This was also Masatsugu Minami's finding, in April.)
1.2 White clouds
Equatorial Cloud Banding seemed progressively less prominent during the
period reviewed, though traces of it were still present in the longitudes E.
of Syrtis Major in early June. On mid-disk the bluish 'Syrtis cloud' has been
seen in the evening and morning, though smaller by late May than in April or
earlier, and not lasting as long into the martian day. With the decline of
equatorial white cloud generally, Syrtis Major was easier to see in violet
light. Ophir-Candor often showed up as a bright streak on mid-disk.
The SPH has seemed bright, progressively becoming more or less continuous
across the S. limb, enveloping Phaethontis, Electris, Eridania, Ausonia,
Hellas, southern Noachis, Argyre and southern Thaumasia/Mare Australe. Hellas
itself was not as bright as earlier in the apparition according to the OAA.
The OAA commented on the diurnal behaviour of the Thaumasia cloud, as seen on
April 16: Minami found brightness S. of Solis Lacus at CML 68 deg; the
bright cloud passed the CM during CML about 78 to 87 deg; under CML 98 deg.
the cloud was seen to be occupying Daedalia; under CML 109 deg. the W. end
of the cloud passed the CM. In Parker's early June CCD images the polar hood
was constant in latitude across southern Thaumasia and environs at these
longitudes.
Morning and evening clouds appeared over Libya-Isidis (related to the Syrtis
cloud). Chryse-Xanthe remained bright in a.m. or p.m., though by early June
this activity had declined. Small morning and evening clouds were imaged over
Tempe in April and May. The diurnal clouds over Elysium continued to appear,
though they were much less prominent towards the end of the period reviewed.
(On June 10 Parker drew attention to the decline of the orographics in an
email.) A set of observations was made by Minami in the first half of May to
show the daily changes in thick morning mist over Utopia.
Many observers do not send comments with their CCD images. As an example of
what might be written, here are Di Sciullo's notes, in part, for his May 3
images, which relate chiefly to the large number of white clouds then imaged:
"Equipment: Excelsior Optics E-258 10" (25 cm) f/8 Newtonian using eyepiece
projection @ f/47 Starlight Xpress HX-516 CCD camera, True Technologies
Dichroic Filters + IR block. No dark frame, flat fielding or bias correction
applied. Camera operated in "Binned" (low-res) mode. Seeing: Mediocre-Fair;
4-5/10. Low humidity (~ 60%), north wind at 3-6 knots. Integration Times:
610 - 720 nm: 0.20s; 490 - 590 nm: 0.14s; 400 - 510 nm: 0.19s. All images
acquired with 700 - 1200+ nm block filter in line with eyepiece projection
unit. Significant activity in 400 - 510 nm band. Heavy evening haze over
Xanthe Terra, south to Margaritifer Sinus. Northern extent of haze appears
to be southern limit of Mare Acidalium, or approximately Chryse Planitia
area, at roughly same parallel as Viking 1 landing site. Haze is triangular
in shape, coming to a point at an area between Ascraeus Mons, and Hebes
Chasma. Spot cloud observed at this location, north of Valles Marineris and
Syria. Second area of pronounced limb haze showing over Aonia, arcing to
eastern Mare Sirenum. 400 - 510 nm band also showing cloud bank over Tempe
Terra / Acidalia region, along with another bright cloud over extreme
northern Acidalia. Persistent cloud or detached ice cap still present at
perimeter of Olympia Planitia, at extreme northern latitude. Other spot
clouds showing over Alba Patera, a pair over Ascraeus Mons, and a faint spot
over caldera of Olympus Mons. Shield of volcano showing as 'bull's eye' just
west of meridian, demarcated by slight circular darkening in 400 - 590 nm
range, punctuated by central bright spot in mentioned bands. Final faint
hint of morning haze present over Orcus Patera. Odd cloud, dusky blue-green
in color observed near 52 north latitude, 202 longitude, just north-west of
Propontis Complex, and due north of Elysium Mons. Not likely to be a
processing artefact, as careful attention was paid to correct color balance".
1.3 Yellow clouds (dust storms)
MGS returned further interesting observations, including some signs of dust
in W. Valles Marineris, near Melas Lacus: see section 3 below for complete
details. Part of southern Chryse was definitely light in red light on a
number of occasions, and sometimes Chryse was visually yellowish (e.g., to
Warell, May 5, 6 on the morning side of the disk). Although there was no
large event there, small-scale dust activity, perhaps persisting from earlier
in the apparition, seems the inevitable conclusion. In red light (W25 filter)
Cidadao imaged a small bright cloud close to the NPC over Mare Boreum on June
2 (near the CM, with CML 92 deg.). Invisible in the blue images, it had
become more extended to the SE (areographic; e.g., Sp.) towards Baltia by
June 3, and may have persisted a few more days. Nothing of the sort had been
imaged by Cidadao on June 1, albeit under poorer conditions. Observing on
June 3 McKim confirmed the light detached area imaged by Cidadao. It is
provisionally concluded that there was a small dust cloud over Mare Boreum;
it was smaller than the 'HST polar cyclone' (due to white cloud; see below),
and closer to the polar cap. (Without proper filtration the situation about
the cap can easily become confused by the bright areas of white cloud
sometimes surrounding the NPC, these being parts of the newly forming N polar
hood. These latter areas are brighter in blue light.)
The OAA Communications In Mars Observations No. 217 (1999 May 10) reported
still another yellow streak associated with Valles Marineris. On April 16
under CML 48-58 deg. in good seeing Minami (20-cm OG, Fukui City Observatory,
Japan) found a light (but not brilliant) yellowish slit streak which
separated Margaritifer Sinus from Mare Erythraeum. After a hiatus caused by
bad weather, OAA observer Akutsu imaged a faint segment between Erythraeum
and Eos on April 20.
I also received yellow cloud alerts for Tempe (more than one observer),
Arcadia and Cydonia, and am still assessing the data to see if the
timecourses of any phenomena may be detailed. At the same time I get the
distinct impression that too many observers are trying too hard to discover
dust storms!
1.4 North polar region
The NPC remained static in size, as far as could be seen without making
precise measurements. Hyperboreus Lacus was large and dark. Chasma Boreale
was seen visually by Tom Cave, Warell and others, and Olympia was widely
reported or imaged throughout the period under review. Around the cap the
amount of polar haze increased, so that sometimes the NPC had a more diffuse
whitish surround. This was especially noticed by Walter Haas, Mario Frassati
and the Director. At other times and longitudes discrete bright spots of
polar cloud were seen, and MGS images were released in both static and movie
format showing the motions of some wispy streaks about the NPC remnant. The
HST imaged what the Space Telescope Institute Press Release termed a 'polar
cyclone' on April 27 (see section 2 for details). There was also a smaller
dust cloud near the NPC (see section 1.3).
2. Hubble's 'polar cyclone', April 27
HST observations of the so-called 'polar cyclone' were obtained on April 27,
and were described by the following Press Release (STScI-PRC99-220) dated May
19. (Figure references are to pictures on the WWW page):
"Hubble Views Colossal Polar Cyclone on Mars
[left]: Here is the discovery image of the Martian polar storm as seen in
blue light (410 nm). The storm is located near 65 deg. N latitude and 85 deg.
W longitude, and is more than 1000 miles (1600 km) across. The residual north
polar water ice cap is at the top of the image. A belt of clouds like that
seen in previous telescopic observations during this Martian season can also
be seen in the planet's equatorial regions and northern mid-latitudes, as
well as in the southern polar regions. The volcano Ascraeus Mons can be seen
as a dark spot poking above the cloud deck near the western (morning) limb.
This extinct volcano towers nearly 16 miles (25 km) above the surrounding
plains and is about 250 miles (400 km) across.
[upper right]: This is a color polar view of the north polar region, showing
the location of the storm relative to the classical bright and dark features
in this area. The color composite data (410, 502, and 673 nm) indicate that
the storm is fairly dust-free and therefore likely composed mostly of water
ice clouds. The bright surface region beneath the eye of the storm can be
seen clearly. This map covers the region north of 45 degrees latitude and is
oriented with 0 degrees longitude at the bottom.
[lower right]: This is an enhanced orthographic view of the storm centered on
65 deg. N latitude, 85 deg. W longitude. The image has been processed to
bring out additional detail in the storm's spiral cloud structures.
The pictures were taken on April 27, 1999 with the NASA Hubble Space
Telescope's Wide Field and Planetary Camera 2.
Credit: Jim Bell (Cornell U.), Steve Lee (U. Colorado), Mike Wolff (SSI), and
NASA"
This event was also the subect of a strange note in BAA Circular 771, in
which it was unfortunately described as a dust storm. The note did not
originate from the Director, who had not been consulted about it. So what did
the ground-based observers actually see?
I received several images and sketches which showed this phenomenon,
including one by myself on April 27, when I found Iaxartes invisible, and the
area between Hyperboreus L. and M. Acidalium to be light. The same day, Cliff
Meredith caught the cloud on a (low resolution) CCD image. The best
ground-based image I have received is due to Cidadao, who caught the cloud on
April 28 under a CML of 88 deg., when it had become a less impressive E-W
whitish streak. Remnants of what may have been the same cloud showed up on
his May 3 image (CML about 119 deg.), though by then the identity of the
white patches had become questionable. This longitude band was not observable
from the USA at the critical time, but the Japanese observers could catch the
E. end of the phenomenon on the morning side of the disk. OAA observers
established that morning cloud over Baltia, between M. Acidalium and
Hyperboreus Lacus, developed from April 25 onwards; they were able to follow
the phenomenon till the 29th.
Such polar clouds have been known for many years of course; ground-based
observations of identical features were made in 1997, for example. What was
exceptional in the present case was the resolution achieved in the HST images.
3. MGS views dust in Valles Marineris
Amongst the more breathtaking images released onto the WWW site by MGS, there
has been an image dated May 16 showing atmospheric dust in the Valles
Marineris. It will be recalled that this site has been active twice already
this apparition (see earlier Mars Section Circulars). Given the chance
viewing of any single site by the MGS cameras, it seems unlikely that it
would catch a storm at its onset. Perhaps more likely is that the billowing
dust was raised from the latter of the two previous events, and was imaged
slowly settling rather than rising. MGS only shot one image on one date, so
no more can be concluded. None of this small-scale detail could be seen by
the BAA team, so the activity was too small to be viewed from Earth: though
Don Parker and others turned in fine detailed CCD shots of the albedo
features and large-scale diurnal clouds around the Valles Marineris, these do
not show any fine-scale tonal differences in the canyon system during May. In
particular, Don's images revealed no changes there during May 3 to 14. After
May 14 our colleague from Florida lost the area at the morning terminator.
Nothing was reported by any ground-based astronomers. Here is the full text
from the WWW site:
"May 1999 Dust Storm in Valles Marineris: MGS MOC Release No. MOC2-130, 27
May 1999
Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC) captured this view of
a dust storm within the Ius and Melas Chasms of the Valles Marineris trough
system on May 16, 1999.
The dust storm is seen in the lower 1/3 of the image. It occurs at the
junction between eastern Ius Chasma and western Melas Chasma. The apparent
motion of the storm is approximately from the south (bottom of image) toward
the north. The dust cloud forms a sharp front along its northern margin,
which is seen along the north wall of Ius and Melas Chasms---in fact, at the
time the image was taken, the dust had advanced up over the north wall of
Melas Chasma (upper portion of lower right third of image) and was advancing
across the upland that separates this chasm from western Candor Chasma. For a
clear-atmosphere view of western Candor and Melas Chasms, see 'Western Melas
and Candor Chasms, Valles Marineris, MOC2-105, 25 March 1999'.
For scale, note that the large crater south of Hebes Chasma, Perrotin, is
about 95 kilometers (59 miles) across. Bluish-white clouds in the image are
interpreted to consist of water ice. The pink/red clouds of the dust storm
occur closer to the ground, at a lower altitude than the water ice clouds.
One of the most interesting aspects of this dust storm is that Valles
Marineris was observed to have a dust storm at exactly the same time of year,
one Martian year ago. During its approach to Mars, MOC obtained a picture of
the planet on July 2, 1997, just prior to the Mars Pathfinder landing. At the
time, it was winter in the southern hemisphere, and dust clouds were observed
within Valles Marineris. The picture is seen in "Mars Orbiter Camera Views
Mars Pathfinder Landing Site, MOC2-1, 3 July 1997". It will be interesting to
see if similar storms occur within the Valles Marineris 1 and 2 Mars years
hence. The next times will be in early April 2001 and mid-February 2003."
The BAA Mars Dust Storm Memoir
I am now busy correcting the first proofs, and the printers hope to publish
by early August. It is hoped that the next Circular will contain details of
price, ordering information and a copy of the Contents page. An advertisement
will appear in the BAA Journal. I am very pleased with the appearance of the
text and colour cover.
Past Reports of the BAA Mars Section
I am sometimes asked for details of these reports, so it may be useful to
give the information here. This information, together with a complete guide
to the telescopic literature for 1659 to 1993, will also be published in the
Memoir. (I suspect my nice tidy columns will become scrambled in the emailed
version of this Circular!)
(JBAA J. Brit. Astron. Assoc.; MBAA Mem. Brit. Astron. Assoc. *
preliminary report; ** brief note(s) only)
Year of oppositionCompiler(s) of reportReference(s)
1892E. W. Maunder*JBAA, 3, 49 (1892)
MBAA, 2, part 6 (1895)
1894B. E. Cammell*JBAA, 5, 148 (1895)
B.E. Cammell & N. E. GreenMBAA, 4, part 4 (1896)
1896E. M. Antoniadi*JBAA, 7, 54=9655 (1896)
*JBAA, 110=96114, 245=96248 (1897)
MBAA, 6, part 3 (1898)
1899E. M. Antoniadi*JBAA, 9, 156=96158, 367=96371
(1899)
MBAA, 9, part 3 (1901)
1901E. M. AntoniadiMBAA, 11, part 3 (1903)
1903E. M. AntoniadiMBAA, 16, part 4 (1910)
1905E. M. AntoniadiMBAA, 17, part 2 (1910)
1907E. M. Antoniadi*JBAA, 18, 398 (1908)
MBAA, 17, part 3 (1910)
1909E. M. Antoniadi*JBAA, 19, 427 (1909)
JBAA, 20, 17, 22, 25, 78,
136, 189, 192, 469, 525 (1909=9610)
MBAA, 20, part 2 (1915)
1911E. M. Antoniadi*JBAA, 22, 452 (1912)
MBAA, 20, part 4 (1916)
1914E. M. AntoniadiMBAA, 21, part 3 (1919)
1916E. M. AntoniadiMBAA, 21, part 4 (1920)
1918H. Thomson*JBAA, 29, 44 (1918)
MBAA, 26, part 1 (1924)
1920H. Thomson*JBAA, 32, 48, 86 (1921)
MBAA, 27, part 1 (1927)
1922W. H. SteavensonJBAA, 32, 330 (1922)**
(See note 1.)
1924W. H. Steavenson JBAA, 34, 348 (1924)**
(See note 2.)
1926W. H. Steavenson JBAA, 36, 324 (1926)
JBAA, 37, 344 (1927)**
JBAA, 39, 145 (1929)**
(See note 3.)
1928W. H. Steavenson JBAA, 39, 145 (1929)**
(See note 4.)
1931B. M. PeekJBAA, 41, 442 (1931)**
(See note 4.)
1933R. L. Waterfield*JBAA, 43, 240 (1933)
(See note 4.)
1935R. L. Waterfield JBAA, 45, 347 (1935)
(See note 4.)
1937R. L. Waterfield JBAA, 47, 351 (1937)**
(See note 4.)
1939R. L. Waterfield JBAA, 49, 378 (1939)**
(See note 4.)
1941R. L. Waterfield JBAA, 51, 350 (1941)**
P. M. Ryves
& A. F. O'D. AlexanderMBAA, 37, part 1 (1951)
1943P. M. RyvesJBAA, 54, 182 (1944)**
(See note 4.)
1946P. M. RyvesJBAA, 56, 155 (1946)**
(See note 4.)
1948P. M. RyvesJBAA, 58, 239 (1948)**
(See note 4.)
1950P. M. RyvesJBAA, 60, 216 (1950)**
(See note 4.)
1952P. M. RyvesJBAA, 62, 253 (1952)**
(See note 4.)
JBAA, 64, 338 (1954)**
(See note 4.)
1956E. H. Collinson *JBAA, 67, 123=96124
(1957)
JBAA, 68, 142 (1958)
1958E. H. CollinsonJBAA, 70, 252 (1960)
1960E. H. CollinsonJBAA, 73, 23 (1963)
1963E. H. CollinsonJBAA, 75, 171 (1965)
1965E. H. CollinsonJBAA, 77, 202 (1967)
(See note 5.)
1967E. H. CollinsonJBAA, 79, 53 (1969)
1969E. H. CollinsonJBAA, 81, 49 (1970)
1971E. H. Collinson*JBAA, 82, 172 (1972)
JBAA, 83, 283 (1973)
1973E. H. CollinsonJBAA, 85, 336 (1975)
1975E. H. CollinsonJBAA, 88, 504 (1978)
1978E. H. CollinsonJBAA, 90, 560 (1980)
1980R. J. McKimJBAA, 94, 197 (1984)
1982R. J. McKim*Inner Planets Newsletter,
Nos. 8, 9 (1983)
*JBAA, 93, 175=96176 (1983)
JBAA, 96, 36 (1985)
1984R. J. McKim*Inner Planets Newsletter,
Nos. 11, 12 (1984)
*JBAA, 94, 271 (1984)
JBAA, 97, 139 (1987)
1986R. J. McKim*JBAA, 96, 256; 97, 2 (1986)
JBAA, 97, 181, 191=96192 (1987)
JBAA, 99, 215 (1989)
1988R. J. McKim*JBAA, 98, 336=96337 (1988)
JBAA, 99, 2=963, 52=9653, 115,
154=96155 (1989)
JBAA, 101, 264 (1991)
1990R. J. McKim*JBAA, 101, 73 (1991)
JBAA, 102, 248 (1992)
1993R. J. McKim*JBAA, 102, 312=96313 (1992)
JBAA, 103, 58=9659 (1993)
JBAA, 105, 117 (1995)
1995R. J. McKim*JBAA, 105, 157 (1995)
1997R. J. McKim*JBAA, 107, 5, 61, 114=96115,
175=96176, 231=96232 (1997);
108, 243=96246, (1998)
*Mars Section Circular Nos.
1=9614 (1996=9697)
1999R. J. McKim* Mars Section Circulars
(1998-99)
Notes:
1. 1922: Some observations by BAA observer P. M. Ryves appeared in the Mars
Reports by Pickering.
2. 1924: Steavenson's personal observations were published in the Greenwich
Observations for 1924. Some observations by BAA observers appeared in the
Mars Reports by Pickering. See also the various reports of the BAA Meeting
discussions.
3. 1926: Some observations by BAA observers appeared in the Mars Reports by
Pickering. See also BAA Meeting discussions.
4. See also BAA Meeting discussions. Until ca. 1935, some observations by
BAA members appeared in English Mechanic.
5. 1965: from this year onward, some BAA observers also sent work for
publication in The Astronomer magazine, but little Mars work has been
published there since the early 1980s.
An old drawing by E.M. Antoniadi
Peter Hingley has published one of Antoniadi's coloured Mars drawings in the
RAS magazine, Astronomy & Geophysics. This drawing is in the RAS archives
(see the 1999 June issue, page 7, where, oddly, north is uppermost). I
published a black and white version of the same drawing (dated 1909 September
20) in my biographical study of Antoniadi, which Peter refers to. Antoniadi
published some of his 1909 drawings in colour during his lifetime, but such
reference sources are not readily available today.
Pages from Pathfinder (and MGS!)
In the same issue of the RAS magazine, page 6, the editor notes the
availability of a special section (576 pp) of the 1999 April 25 issue of
Journal of Geophysical Research devoted to the Pathfinder results. The
principal scientific results include discoveries of:
"* the spin pole and precession rate of Mars since Viking, 20 years ago;
results require a central metallic core of radius between 1400 and 2200
kilometres;
* evidence of warmer and wetter times in the past;
* a dusty lower atmosphere where 'dust devils' are common;
* ice clouds are common in the early morning, and morning near-surface
temperatures change abruptly with time and height."
On page 4, same source, the magazine's Editor briefly discusses the 'magnetic
stripes' discovered by MGS on parts of the martian surface, and the possible
implication of past tectonic activity by analogy with the stripes on Earth's
ocean floors, caused by crustal spreading.
BAA Exhibition Meeting
UK members may wish to know that I will be displaying some of the Section's
work at the BAA Exhibition Meeting later this month. This is the first time I
have been able to attend in person since my term as BAA president (1993-95),
so I am looking forward to meeting old and new friends.
Reporting data to the Section
I am always happy to receive CCD images by email. Any URGENT and important
drawing can be scanned and sent as an image file, but I do not want to
receive routine drawings by email, because the vast majority are sent to me
as hard copies, and that is the form I like to compare (and archive) them in.
I have to again write that I am spending a disproportionate amount of time
downloading files sent to me over the Internet, then decoding, analysing and
refiling them in the Section's records! Send mail to Cherry Tree Cottage, 16
Upper Main Street, Upper Benefield, Peterborough PE8 5AN, Great Britain; home
telephone 01832-205387; home email Rmckim5374@aol.com. (Do not use the former
email address for my place of work (mckim@oundle.northants.sch.uk).) Urgent
faxes can be sent to my place of work on 01832-274052.
The next Circular
Please report the June observations by July 10, so that the next circular can
be issued by mid-July.
Good observing!
Richard McKim, Director, 1999 June 20th
Back to Date Menu
March 1 - April 15, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 5
General
This Circular summarises the period 1999 March 1- April 15. On Mar 1, Ls =
104 deg., D = 10 arcsec., lat. of centre of disk = 15 deg. N, with the
planet's declination at 13 deg. south. The planet will reach opposition on
April 24 (Ls = 129 deg., D = 16 arcsec., lat. of centre of disk = 18 deg. N,
decl. -12 deg.). The planet was becoming uncomfortably low for UK observers,
but as can be seen, its declination will now be very slightly less southerly.
The UK weather has been less than cooperative during opposition month, but
nevertheless there have been a fair number of observers, including the usual
contributions from overseas that are essential to maintain good longitudinal
coverage. During the present apparition I have had observational data from
the following individuals, and acknowledge it herewith if not already done so
by letter or by email: Leo Aerts, Sally Beaumont, Nicolas Biver, Ed Crandall,
P.Devadas, Mario Frassati, Martin Gaskell, David Gray, Peter Grego, Walter
Haas, Alan Heath, Carlos Hernandez, Frank Melillo, Cliff Meredith, Masatsugu
Minami /OAA, Patrick Moore, Don Parker, Damian Peach, Tom Richards, Richard
Schmude, David Strange, Paolo Tanga, Gerard Teichert, Rowland Topping, Dan
Troiani/ALPO, Johan Warell, Sam Whitby and Jonathan Wojack.
More than one observer has supplied unreadable CCD image files: I do not
always have the software to decode compressed files, and it would sometimes
save time to mail a disc. I would also kindly point out to observers that I
do not always have time to look for images on their personal Websites, much
as I would like to; if you want your images discussed in these reports,
kindly send them along in a readable format!
I am sorry that Dr Ebisawa's health has not been very good, so that he has
not been able to make his usual meticulous visual and polarimetric
observations so far. Is anyone doing polarimetric work this apparition?
Observations
On Mars throughout March and April the N. polar cap remained small. A number
of visual and CCD observations show haze around its S. perimeter. Despite
this haze the outlying bright area of Olympia has been visible. Tanga saw it
from Turin Observatory in fine seeing on April 18. White cloud activity
remains quite high, but the Equatorial Cloud Band phenomenon (ECB) seemed
much less conspicuous in April. The typical sites for white clouds have been
active throughout the whole period, and a few observations will suffice to
illustrate these locations and to describe some other features:
McKim, April 13, 22-cm refl., 2318h UT, CML = 218 deg. Elysium on mid-disk
whitish. Bright am cloud over Libya-Isidis (and Syrtis Major). Hellas a
brighter spot within the light S. limb area. Cebrenia lightish on the CM,
some haze S. of NPC, but cap edge sharp. Some pm cloud over Amazonis, but Nix
Olympica would have rotated off the disk at an earlier hour. The Aetheria
secular darkening remains extensive and dark, and extends somewhat to the SW
as in the last few apparitions. Propontis (I) is dark, and the
Phlegra/Styx-Trivium Charontis-Cerberus complex, though not dark, was easy to
see.
Meredith, April 14, 22-cm refl., 2355h UT, CML = 218 deg. CCD image much like
McKim's visual drawing above. (Cliff's first really successful CCD work,
well done to him.)
Parker, March 7, 0.4-m refl., ca. 0735h UT, CM = 321 deg. Evening cloud dims
Syrtis Major, extending across it from Libya to Aeria! The evening Hellas is
bright. Morning cloud occupies Chryse and partly hides SW Mare Acidalium.
Haze south of the NPC.
Parker, March 12, ca. 0803h UT, CML = 282 deg. Hellas is very bright in white
light. As Minami points out in the OAA's CMO, the brightness sometimes
extends outside the contours of the basin: Gray found a similar phenomenon
with Argyre in January.) Hellas was large and bright in green (VG9 filter)
and blue (BG12), but was smaller and paler in red (RG610).
Parker April 3. This CCD image series even shows a little structure inside
the Solis Lacus (which remains large and dark since the mid-'80s). The
feature Gallinaria Silva, a small dark spot that was seen to the W. of the
Solis Lacus in the apparitions immediately before the present one, seems to
have nearly disappeared. This is therefore perhaps a small change since 1997.
There is really fine structure in the Tithonius Lacus between Melas Lacus and
Noctis Lacus! Aurorae Sinus appears detailed, with little northward
projections including Baetis/ Juventae Fons, etc. Mare Acidalium and Niliacus
Lacus are shown in fine detail. Hyperboreus Lacus is a dark spot adjacent to
the small NPC.
Teichert, April 10, 28-cm SCT, 0056h UT, CML = 277 deg. Hellas bright on the
CM. Nepenthes is invisible. Moeris Lacus forms a small protrusion on the E.
side of Syrtis Major.
I do not intend a more complete analysis here. UK members may wish to know
that I will be showing some illustrations of the Section's work in my
presentation at the BAA Northampton Meeting on Saturday April 24.
Pic du Midi Website
This is an excellent site (http://www.bdl.fr/s2p/mars.html), and contains
some medium to high resolution images of Mars (1988-1999).
LPL Mars Water Group
Ann Sprague emailed with more details of her LPL Mars Water Group's work at
Catalina: see Rik Hill's communication from the same group in the last
Circular. Anne writes that they have been measuring water vapour in the
martian atmosphere every two weeks since 1998 September. "We are measuring
CO2 molecular absorption with the hopes of using radiative transfer to
measure atmospheric dust... the depth of the water vapor absorption line in
Mars' Northern latitudes is much deeper than we have seen it in previous
Northern summers."
February dust storm follow-up
Last time's Circular detailed a Regional storm over the Mariner Valley, whose
observation was mostly due to David Gray. Todd Clancy emailed on March 10 to
report that this event (which had first been detected on February 21) had had
no apparent effect upon the atmospheric temperature (as deduced from radio
waveband work), but, interestingly: "the overall trend in temperatures over
the past two months is 5-10 K warmer than at this time in the previous Mars
year." For those wishing to see David Gray's two sketches of the event, they
may now do so thanks to Don Parker who scanned them and uploaded them to the
Marwatch Website. Steve Lee emailed descriptions of the HST images of March 3
(CML 256, 280 deg.): these revealed ECB, but the CML was too high for them to
show the Valles Marineris area.
Note that the results of Ann Sprague's spectroscopy and Todd Clancy's work
seem to fit nicely together! It will be interesting to see if this relates to
the regression rate for the NPC.
Yet more dust over Valles Marineris!
A further event occurred during the Director's absence on holiday abroad.
Upon his return home on April 11, awaiting him was an email and observation
by Carlos Hernandez, dated March 31 (22cm refl., CML = 53 deg.), which
revealed an already mature dust storm in progress, in the form of a bright
streak running E-W along (the S. edge of?) Valles Marineris. At first sight I
thought it might just have been residual dust (see my comments upon Don
Parker's March 3 CCD image in the last Circular), but Carlos had not noticed
it earlier, and, moreover, it was too prominent, too well defined, and was
bright through a W23A red filter. In his email Carlos mentioned that a CCD
image by Antonio Cidadao taken 1h earlier had also shown the bright streak.
Carlos observed again a few days later on April 2, finding that the area had
returned essentially to normal. So when did it begin? Several days later,
David Strange emailed a good CCD image taken on March 27 at 0100h UT under
CML = 43 deg. This showed a bright area in Ophir which interrupted the
Agathodaemon (also known as Coprates, part of W. Valles Marineris: a
classical 'canal' which runs between Aurorae Sinus (Planum) and Tithonius
Lacus (Chasma)). This was most probably the initial cloud of the storm, and
the event subsequently spread eastward along the canyon. Don Parker's CCD
images of April 1 show the area, but in very bad seeing; his work on April 2,
3 and 6 is high resolution, but apart from a possible faded appearance of
Aurorae Sinus, the area seemed normal. Warell observed from Uppsala
University Observatory, Sweden, with a 16-cm OG: on March 29, 30 and April 1
(CML = 23-34 deg.) he found a large am cloud over Tharsis and Thaumasia,
etc., to appear distinctly yellowish. Johan's seeing conditions were not good
enough for him to see the dust actvity in the Valles Marineris, but the
yellow tint could represent dust diffused from the minor storm then underway.
Ditto April 5, under CML = 322 deg., when a yellow tint was evident in the
Chryse-Xanthe am cloud. In any case, a short-lived event.
Does anyone else have pertinent observations? If so, kindly let the Director
know! Looking at the Pic du Midi website will reveal a March 24 image which
does not show the storm, so we appear to have pinned it down quite well. The
location of the 1984 June Regional storm fell in a similar location; in that
case, dust also spread to the east over the same area, as well as dispersing
generally over Mare Erythraeum. This storm was fully described in the
writer's published 1984 BAA apparition report.
The Director looked up the work of the group that are analysing solar radio
occultation data from MGS to determine atmospheric temperatures. There is a
section on the MGS homepage. Joe Twicken of that group kindly (and rapidly)
responded to a query from the Director with the following email. " We have
not processed the raw data that we do have for the dates that you mention. We
do have a lot of data from the February period, but very little from the
March period. MGS did not begin normal mapping operations until this month.
Precise reconstructions of the spacecraft orbit are required to process our
raw data, and the orbit reconstructions from JPL for the February and March
periods were not sufficiently accurate for us to retrieve meaningful
atmospheric profiles. Other members of our Team are in the process of
reconstructing the orbits, and we will process the data when we can. I will
let you know if we see anything interesting. You should be aware that the
spacecraft occultations during the periods you mention occurred at very high
northern and southern latitudes, so we will not have any atmospheric data
from the vicinity of Valles Marineris." Thus it seems that the only record
of the March storm is again that of the groundbased observers. Keep up the
good work, everybody! But for your observations, these two small but
important events would have been completely missed!
Mars as seen through the eyes of the Global Surveyor
MGS has begun to image the planet from orbit again, after achieving final
orbit about March 1. In the current (May) Sky & Telescope Jonathan McDowell's
Mission Update column mentions a dramatic incident at Mission Control which
nearly interfered with the attainment of the final orbit...
Since the release of the Aerobraking Image Set, the MGS website has been
posting full-disk and closeup images from March and April. These show how
successfully the craft is behaving, and whet the appetite for more! Polar
dune fields, craters, clouds, Valles Marineris (including a fine shot of E.
Tithonium Chasma, image MOC2-109)... But telescopic observers will be most
interested in two full-disk 'images', reconstructed from a sequence of nine
strip-maps obtained on successive orbits. These were obtained in March during
the calibration phase of the mission. The Director has emailed for a more
precise date in case the images can support the discussion of the latest
Valles Marineris dust storm. The colours will not be perfect as the Martian
Orbiter Camera (MOC) makes red and blue images, and averages them to make
a 'green' image to combine with the others to make a colour composite. Another
consequence of this process would seem to result in rather low albedo
contrast compared with that telescopic observers can enjoy. (No matter, just
try Adobe Photoshop or similar program on your PC, and you can make them look
more like telescopic images - and put south at the top at the same time!!)
MOC2-117 shows Syrtis Major central, partly covered by the bluish-white 'Syrtis
Cloud'. Iapigia shows the location of the large Huygens crater.
Hellas is bright and looks mostly (but not entirely) frost-covered. The NPC
shows fine rifts and the broad dark Chasma Boreale (Iaxartes). The fine
albedo details around Utopia-Boreosyrtis-Propontis look to be very similar
(if not identical) to 1997, as 1997 looked identical to 1995 in the HST
images.
MOC2-118 is an image of the Tharsis and Thaumasia regions. The morning clouds
cover Olympus Mons, Alba Patera, Ascraeus Mons, but affect Pavonis and Arsia
Mons less.
The Mars Dust Storm Memoir
At last I can report that everything is finished and checked, and that I will
be taking the text and figures to the printer, University Printing Services,
Cambridge (the printers of the BAA Journal), in the next couple of days. It
is to be hoped that it can be published in the next few months. The printed
text will occupy about 168 pages, equivalent to THREE 56-PAGE ISSUES of the
Journal!
Reporting data to the Section
I am always happy to receive CCD images by email. Any URGENT and important
drawing can be scanned and sent as an image file, but I do not want to
receive routine drawings by email, because the vast majority are sent to me
as hard copies, and that is the form I like to compare (and archive) them in.
I have to write that I am spending an enormous amount of time downloading
files sent to me over the Internet, then decoding, analysing and refiling
them in the Section's records! Send mail to Cherry Tree Cottage, 16 Upper
Main Street, Upper Benefield, Peterborough PE8 5AN, Great Britain; home
telephone 01832-205387; home email Rmckim5374@aol.com. (Do not use the former
email address for my place of work (mckim@oundle.northants.sch.uk).) Urgent
faxes can be sent to my place of work on 01832-274052.
The next Circular
Please report observations April 16 to May 31 by June 7, so that the next
Circular can be published in the second or third week of June.
Good observing!
Richard McKim, Director, 1999 April 23 (Opposition Day minus one!)
Back to Date Menu
February 1-28, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 4
General
This Circular summarises the period 1999 February 1-28 (but with an incursion
into early March). On Feb 1, Ls = 91 deg., D = 7.9 arcsec., lat. of centre of
disk = 18 deg. N, with the planet's declination at 10 deg. south, some 5
degrees lower in the N. hemisphere skies than last month!
At my suggestion Jim Bell included Circular No. 3 in the last Marswatch
Electronic Newsletter, with a circulation of 1455 (only 1355 more than mine).
More good news is that next month marks the start of the main mapping mission
of Mars Global Surveyor. The craft has achieved its final, more circular
orbit, and will hopefully take many hi-res images. On the MGS webpage there is
now the 'Aerobraking Image Set' available for viewing and downloading.
Recommended.
National Geographic has just published a new Mars book with many recent
images. I have not seen it, but surely it will soon be out of date! (I am
hoping somebody will send me a Review copy!) A general interest article by
A.D.Andrews in the Irish Astronomical Journal was copied to me by Tony Kinder,
BAA Librarian. Titled 'The Leviathans of Tharsis' its scope is self-evident,
but I was surprised to find the BAA 1986 map, one drawing by myself, and
several other drawings by past BAA observers used as illustrations (Reference:
26 (1), 45-64 (1999)). John Rogers draws attention to several pieces in Nature
for 1999 February 18 (397, 560, 584, 586, 589 and 592) dealing with volcanism
on the early Mars, recent volcanism deduced from crater counts, dune-fields,
etc., as revealed by the MGS spacecraft during the early phase of its mission.
On Mars throughout February the N. polar cap appeared rather small, and at
some longitudes the dark rim seemed hard to see, or was absent. Parker's CCD
images sometimes showed some white haze just S. of the NPC, and this was the
case in the most recent images of March 3 (CM = 5-12 deg.). White cloud
activity presently remains high, and the Equatorial Cloud Band phenomenon
(ECB) has been very conspicuous in the CCD images, especially in blue light.
Elysium was brighter in the afternoon, and Hellas brightened considerably in
early February, being markedly lighter than in the previous month, sometimes
with a brighter spot in its NW corner. The 'Syrtis Blue Cloud' has been imaged
again by Parker. More observers are becoming active, and are sending in work:
thanks to S.Beaumont, A.W.Heath, Dr T.J.Richards and Dr R.Topping for recent
contributions.
Rik Hill emailed to say that his group at LPL were observing the planet every
fortnight (primarily to monitor atmospheric water vapour) with the 61-in
telescope at Catalina. He reports: "Our observations indicate the possibility
of enhanced dust south during the period a week to either side of 1 Feb." The
Director emailed early data about the Valles Marineris storm reported below,
although this event occurred a little later in February, as will be seen. I
have asked Rik for more details of his work.
Dust storm over Valles Marineris!
Rather than report the mundane, this month's Circular is devoted to the story
of a regional dust storm which was observed in the second half of February. On
February 21 David Gray (42-cm Dall-Kirkham Cass., with x262-x415, Spennymoor,
County Durham, Great Britain) observed considerable obscuration of the
markings and kindly notifed me at once by telephone. I immediately issued an
email alert to about 20 observers in Europe, the USA, Australia and Japan, and
telephoned several UK observers who are not on email. The response was
gratifying, although I have had no news from Japan as this issue goes to
press. Although we may not have caught the precise start of this regional
event, its decline and fall (as Gibbon might have written) was well followed.
I recently emailed Todd Clancy to ask whether the dust has had any measurable
effect upon martian atmospheric temperatures, as revealed through his radio
waveband work. Selected details of the observations follow:
Feb 19, 0700-0730 UT, CM = 101-108 deg, D.C.Parker, visual, 15-cm refl., from
Chiefland, Florida: Don emailed this observation after hearing about the
storm. He may have witnessed its start by noting a bright cloud on the
terminator: "It was very bright in integrated and blue light, but not
especially bright in red. On one occasion of excellent seeing, however, I
thought it had a peculiar hook shape, reminiscent of dust". This must have
been over Xanthe at the CML quoted, perhaps close to Aurorae Sinus. (I await
sight of Don's sketch.)
Feb 19, 1756 UT, CM = 261 deg, T.J.Richards (Victoria, W. Australia): A nice
CCD image with his 18-cm OG, showing the Syrtis Major side of the planet
completely normally and in fine detail.
Feb 21, 0210-0300 UT, CM = 12-24 deg, D.Gray: Most of the SW (S. following)
part of the disk was distinctly light, even in poor moments of seeing. A
brighter, elongated core was seen, especially in red (W25). This core was like
a 'V' on its side, with the apex occupying the N. part of Margaritifer Sinus,
one fork running along or close to the Valles Marineris, and the other running
off towards the SW limb, covering part of Mare Erythraeum. Margaritifer Sinus
was quite invisible. Sinus Sabaeus was well-marked, but the 'Forked Bay' area
(Sinus Meridiani) and the S. part of Mare Acidalium both seemed a little
obscured too. A more diffuse brightness covered the equatorial deserts from
the CM westward (Chryse, Xanthe, etc.), and this region was bordered on the E.
by a dusky curving streak. Nothing could be seen of Aurorae Sinus to the west.
Seeing was almost continually good throughout.
Feb 21, 0600 UT, CM = 68 deg, Hernandez (USA): N. Margaritifer Sinus and Mare
Erythraeum are faint. Agathodaemon (W. half of Valles Marineris, between
Aurorae Sinus and Tithonius Lacus) is dark. Chryse-Xanthe bright in red light.
To the west, Solis Lacus is dark, and that region appears normal. (I have not
yet seen the drawing made by Carlos; it was most useful that he observed a few
hours after Gray, so that his observation places limits on the W. side of the
dust storm.)
Feb 22, Gray: Very windy and with poor seeing. Mare Acidalium on the CM.
Bright cloud is again seen from about the CM to the following limb.
Feb 22, CM = 126-128 deg, F.J.Melillo (USA): Near-blank red light CCD images,
but on a small scale, and at too high CML to catch the storm.
Feb 23, 0520 UT, CM = 40 deg, Gray: In fine seeing he found the Aurorae Sinus
area very faint (and it is drawn very ill-defined), but the Margaritifer Sinus
and Mare Erythraeum regions have darkened again, and are as dark as M.
Acidalium. Agathodaemon is dark, as is Solis Lacus. Chryse-Xanthe is light, as
is the whole of the following part of the disk: Candor, Tharsis, Tempe. All
this light cloud has rendered Nilokeras faint, and Ganges nearly invisible. By
0600 UT the Chryse-Xanthe area was less bright. As ECB had been observed in
these longitudes before the event, there was probably a mixture of white cloud
and dust.
Feb 23, CM = 119 deg, S.Whitby (USA): With a 15-cm refl. Chryse-Xanthe bright
on the evening side, more so in red than in blue, but observer unable to see
anything else due to small aperture.
Feb 24, CM = 81-93 deg, Parker (USA), 41-cm refl., CCD work (and below):
seeing evidently not very good, but Solis Lacus dark. Strong ECB right across
the disk, including the evening Chryse-Xanthe. The Aurorae Sinus region is not
well placed.
Feb 26, CM = 15-25 deg, Gray: The S. features look much as on Feb 23 (Gray),
with Aurorae Sinus still weak. Equatorial cloud present. I have not yet seen
David’s drawing of this date.
Feb 26, CM = 75 deg, Parker: Aurorae S. is present but not dark: seeing is not
very good. ECB evident.
Feb 26, T.Stryk (ALPO, observation passed on to me by Jim Bell): observer
remarked upon the region of Candor-Tharsis, that was bright in red light.
Certainly Candor is also light in Parker's February CCD images generally, but
whether it was enhanced during the storm I have not yet decided.
Feb 27, CM = 52-67 deg, Parker: As Parker, Feb 26.
Feb 28, CM = 33-61 deg, Parker: seeing looks better than on 24, 26, 27.
Aurorae Sinus looks normal in shape, but still perhaps less dark than usual,
as it is definitely not as dark as the (now clearly normal) E-W dark band of
the Mare Erythraeum. The ECB is incomplete at this CML, with some cloud in S.
Chryse-Xanthe, then unconnected cloud over Ophir-Candor-Tharsis on the a.m.
side. What is perhaps significant is that the images show the 'canal' known as
Hydaspes visible as a halftone streak curving its way from the W. side of
Margaritifer Sinus to somewhere about the SW side of Niliacus Lacus. This
feature is rarely seen, though it was recorded as being dark during 1858-1871.
Did it darken by surface excavation at the NE edge of the storm? I wrote the
above description before I read Don's own notes: he independently noticed the
Hydaspes, and drew attention to it.
March 3, CM = 5-12 deg, Parker: good seeing. My impression of this CCD image
is that some residual dust shows up very weakly as a thin E-W streak in red
light just N. of Mare Erythraeum, and that there is a distinctly brighter
cloud (dust) in red light just NE of Aurorae Sinus. Extensive but diffuse
brightness is seen in Chryse-Xanthe (perhaps brightest in red light), and in
Tharsis and Tempe (the latter regions were brightest in green and blue light).
There is an ECB from the p. terminator to the f. limb. The albedo markings
look very nearly normal to me on these images.
In character and evolution the February storm was not very different from
those of 1984 April (Ls = 132), 1990 October (Ls = 308) and 1997 June (Ls =
139), described in past BAA Section Reports by the undersigned. If we accept
the Feb 19 observation as marking the start, the storm was highly active and
near maximum on the 21st, but was already dispersing by Feb 23. On Feb 28 and
Mar 3 only traces of dust remained.
Thus the storm began near Ls = 99 deg., which is seasonally a bit early
compared with former telescopic events which definitely began over Valles
Marineris: my historical research shows that the earlier storms (1924-1990 and
?1879) occurred during the interval Ls = 132-357 deg., with most events near
the extreme limits. On the other hand, events which began in neighbouring
Chryse/Xanthe have occurred in the intervals Ls = 96-225 and 308-344 (from
records between 1903 and 1992), and the 1999 February event thus falls nicely
within the first interval. Anyone else out there with more observations of the
longitudes in question? Steve Lee emailed me to say that his group were to
have obtained time on the HST on March 3, under CM 300 deg., and their results
will be interesting to compare with Parker's on the same date (see above). HST
imaging is to be much less intensive than in 1997 this apparition, as noted in
an earlier Circular: the role of the ground-based observer is again underlined
by the our coverage of the dust event. (And who says it is always cloudy in
Great Britain?)
The next Circular
As I may be out of the country in early April I will attempt to issue a report
covering March 1-April 15 during the third or fourth week of April. Therefore
please report up to April 15 by, say, April 22.
Reporting data to the Section
I am always happy to receive CCD images by email. Any URGENT and important
drawing can be scanned and sent as an image file, but I do not want to receive
routine drawings by email, because the vast majority are sent as hard copies,
and that is the form I like to compare (and archive) them in. Send mail to
Cherry Tree Cottage, 16 Upper Main Street, Upper Benefield, Peterborough PE8
5AN, Great Britain; home telephone 01832-205387; home email
Rmckim5374@aol.com. (Do not use the former email address for my place of work
(mckim@oundle.northants.sch.uk).) Urgent faxes can be sent to my place of work
on 01832-274052.
Richard McKim, Director, 1999 March 7
Back to Date Menu
December 16, 1998 - January 31, 1999
British Astronomical Association
Mars Section Circular 1998-99, No. 3
General
This Circular summarises the period 1998 December 16 - 1999 January 31 (Ls =
71 - 91 deg., D = 5.7- 7.8 arcsec., lat. of centre of disk 24 -18 deg. N). I
have received CCD images from Don Parker, Frank Melillo and Damian Peach;
David Gray remains the most prolific visual contributor. The weather in the UK
has not been very cooperative, but observers have made the most of any fine
weather. From Hawaii Nicolas Biver put his 26-cm reflector to good use on a
few mornings. The OAA CMO 211 described Japanese work during December 16 to
January 15.
The next Circular will discuss observations done in 1999 February, and I
intend to compile it by March 7. Therefore please send any relevant work in
time for it to be included. Most of the Circulars from the last apparition
(and Nos. 1 and 2 from 1998-99) are to be found on the Mars Section website.
There is a new MarsWatch site, now sponsored by the Astronomical League
(http://www.astroleague.org/marswatch/). There is an article about how to
observe the current apparition in the latest copy of the ALPO Journal (1998
October).
I hope to say something about the current round of Mars-bound spacecraft,
later, perhaps in the next Circular.
N. polar region
The cap remains bright and conspicuous, though the latitude of the S. edge has
moved much further north. On January 11 for example, Warell found it to be
"brilliant white". Parker's images (e.g., January 20, under CM = 66-69 deg.)
also show the dark patch Hyperboreus Lacus at the edge of the cap. Though the
tiny disk militates against really detailed study, Parker's CCD work indicated
some detached outliers to the S. of the cap, and detail within the cap itself.
Thus on December 25, CM = 310 deg., the cap had a well-defined brighter patch
following the CM with indications of further structure around the centre of
the cap. This bright spot seems to be a seasonal feature, and it was shown in
Parker's red filtered images as well as in the overall composited colour
views.
The most famous (and largest) seasonal outlier is Olympia. Antoniadi found it
began to be separated from the cap near Ls = 80 and that the outlier could be
followed up to Ls = 195. It is important to try to establish these seasonal
dates for every favourable apparition, as some authorities have considered
them variable from martian year to year. Further, being in fixed topographic
positions, they provide another means of judging the seasonal progress of the
polar cap. Parker's images of January 9 (CM about 170 deg.) imperfectly
resolved Olympia at Ls = 81 degrees. Further observations please!
A new study of the NPC recession from Earth-based and HST data covering the
years 1990 to 1997 has recently appeared in Icarus (136, 175-191 (1998)).
Written by B.A.Cantor, M.J.Wolff, P.B.James and E.Higgs it advances evidence
that the recession rate varied slightly during these four apparitions, the
rate of recession being a bit slower in 1994-95. BAA NPC data from 1993 (and
1980-82) have already been published (R.J.McKim, J. Brit. Astron. Assoc., 105,
117-134 (1995)), and recent (unpublished) analyses of the Section's work for
1995 and 1997 suggests very small interannual differences during 1993-97. It
is clear that the HST images are a quantum advance upon previous Earth-based
work, but being comparatively few in number it is still vital that as many
accurate measures as possible are made by ground-based workers. Cantor et al.
agree with the writer's opinion (expressed in the 1993 Section Report, op.
cit.) that measures of the north cap's E-W diameter involve systematic errors
(due to limb darkening or diurnal clouds) when the contour of the cap is not
located entirely within the visible disk. BAA data have been analysed for the
cap latitude on the CM (N-S direction): visual drawings, filar micrometer data
and measures from photographs, when made by the same method have yielded
comparable results. But comparisons of micrometric data measured in the E-W
sense have not agreed exactly. Thus historical comparisons can present a
problem if the method of measurement has not been stated in the literature. In
the course of his research for the BAA Dust Storm project, among appropriately
dusty archives in both the USA and Europe, the writer found a great deal of
unpublished polar cap data. Another project...? Perhaps.
Atmospheric activity
No clear-cut evidence of dust storm activity has been found so far, but white
cloud activity has increased, and there have been numerous records of the
Equatorial Cloud Band (ECB) effect. The martian orographic clouds over Olympus
Mons (Nix Olympica) and the Tharsis volcanoes have been very clearly imaged
and observed visually. Rather than giving an incomplete preliminary
meteorological report here, some selective notes of the more interesting
observations are given below. All of Parker's work is CCD; the others, visual.
Parker, December 19: CM = 11-18 deg. Chryse-Xanthe is lightish, as is Tempe on
the a.m. limb following M. Acidalium.
Parker, December 23: CM = 341-346 deg. Chryse-Xanthe is light on the morning
side (especially in green and blue light).
Gaskell, December 24: Argyre is bright and bluish on the evening side, and
there is extensive morning cloud over Tharsis to Solis Lacus.
Parker, December 25: CM = 310-318 deg. Hellas on the evening side looks only
vaguely light. A thin ECB is seen across the disk.
Parker, January 1: CM = 250-256 deg. Elysium is light on the evening side.
Hellas is only very slightly white in the morning, and there is some morning
cloud over Aeria following Syrtis Major. In blue light (BG12) the Syrtis is
invisible and the white cloud in Aeria enlarged. In an email Parker reports
having seen the "Syrtis Blue Cloud" visually on this date.
Gray, January 7: CM = 122 deg. Nix Olympica, on the CM, is not especially
light, but is seen to be surrounded by a dark area, especially on the N. side.
(With a phase angle of 36 deg., the local martian time would be about 1.20
pm.) Tharsis, on the evening side, contains extensive bright cloud. The S.
limb was rather light, too.
Parker, January 9: CM = 158 - 178 deg. Orographic clouds over the Tharsis
region on the evening side, somewhat blurred by the seeing. Elysium is well
onto the disk on the morning side and looks bright. (Allowing for phase it
must be near local noon over Elysium.) These bright patches are imaged
especially clearly in blue light.
Gray, January 10: CM =108-113 deg. Light S. limb. Tempe lightish on the p.m.
side. Alba is light, crossing the CM. Nix Olympica on the a.m. side is also
rather light
Warell, January 11: Argyre light on the evening side and extended haze over
Memnonia on the morning side.
Parker, January 15: CM = 107-128 deg. The Equatorial Cloud Band effect is in
evidence both in the blue light images and in the composited colour images. A
bright equatorial cloud on the evening side thins out towards the west, and
runs discontinuously across the disk where it meets a large bright cloud on
the morning limb. The last images show a discrete Nix Olympica very bright
approaching the CM (early afternoon, local martian time). Morning cloud also
completely surrounds Propontis I, a phenomenon noticed in 1997, 95 and 93 (and
illustrated in the 1993 final Section Report). Cebrenia is also hazy.
Gray, January 16: CM = 63 deg. The region just S. of Aurorae Sinus looks
unusually pale as if affected by haze, but observing conditions are not
perfect. On the evening side Chryse-Xanthe is a light region.
Parker, January 18: CM = 87-101 deg. ECB and Nix Olympica again very evident
(blue, green light and in composited colour CCD frames). The evening cloud is
over Xanthe and Candor-Ophir.
Parker, January 20: CM = 66-69 deg. Candor-Ophir is again light on the CM.
Gray, January 21: CM = 355 deg. The S. limb, including Noachis, is very
bright, the brightness extending to encompass the small part of Argyre that is
visible on the a.m. side. On the morning side this cloud extends north over
part of M. Erythraeum. Chryse-Xanthe also bright on the morning side.
Gray, January 22: CM = 353-356 deg. Much as the 21st, but filter work shows
that the a.m. limb part of the S. limb brightness is most conspicuous in blue
and green light. (On both mornings this bright patch rapidly faded with time.)
Surface features
Propontis remains a conspicuous dark spot. Solis Lacus is still large and dark
to Parker, Gray and Biver, as it has been since the mid-80's. It is elongated
E-W. No internal details have been resolved yet. No trace has been found of
the Phasis development to the W. side of Solis Lacus, which is in line with
the gradual fade notice in the last few apparitions. As in 1997 the Cerberus
region is not prominent, but it showed up faintly nonetheless in Parker's CCD
images, as well as in Gray's drawings. Gaskell reports having picked up
internal details in M. Acidalium.
Erratum in Circular No. 2
Apologies to David Gray for wrongly quoting the date of his Libya observation
as December 23: it should of course have read November 23.
Reporting data to the Section
Send mail to Cherry Tree Cottage, 16 Upper Main Street, Upper Benefield,
Peterborough PE8 5AN, Great Britain; home telephone 01832-205387; home email
Rmckim5374@aol.com. (Do not use the former email address for my place of work
(which was mckim@oundle.northants.sch.uk).) You can also send any really
urgent fax to my place of work on 01832-274052.
Richard McKim, Director, 1999 February 7
Back to Date Menu
November 16 - December 15, 1998
British Astronomical Association
Mars Section Circular 1998-99, No. 2
General
Mars remains distant, so that many Section members have yet to begin work.
This Circular summarises the period 1998 November 16 - December 15 (Ls = 58-70
deg., D = 4.9 - 5.6 arcsec., lat. of centre of disk 25 - 24 deg. N), though
some observations a little later and earlier have been added for comparison.
Since publishing Circular No. 1 I have received two more of the OAA's
bulletins (Nos. 209, 210) which cover the periods Oct 16-Nov 15 and Nov
16-Dec 15 respectively. I have received nice CCD images from Don Parker and
Frank Melillo; David Gray remains the most prolific visual contributor. Jim
Bell emailed that HST coverage is unlikely to be extensive in 1999, which
makes our efforts all the more worthwhile.
Please note that all the following data have been obtained on a disk below 6
arcseconds diameter: congratulations to all concerned!
The next Circular will cover the period 1998 December 16 to 1999 January 31,
and I intend to compile it by February 15. Therefore please send any relevant
work to cover that period in time for it to be included. I have sent email or
paper copies of Circulars 1 and 2 to all active Section members from 1997, and
to others who might find it of interest. Inactive Section members may not
receive further copies, please note!
Most of the Circulars from the last apparition are to be found on the Mars
Section website (see http://marswatch.tn.cornell.edu/baa.html).
N. polar region
The cap remains bright and conspicuous (with dark surroundings) though
somewhat reduced in size. Selected measures indicate normal recession. During
the period reviewed no internal details were reported in the cap.
Atmospheric activity
No dust storm activity has been reported, but there is some white cloud
activity, reported in no special order below:
Hellas: Whitish or slightly so at the morning limb, dull thereafter. Patrick
Moore (Nov 17, CML 256-271 deg.) drew it fairly dull. Combined data show that
it began to brighten after CML 280 to 300 deg., becoming very bright by
martian evening (CML about 330 deg.). Gray on Nov 10, just before the period
reviewed, found Hellas very bright at the evening terminator under CML 339
deg., but it had gone off the visible disk by 345 deg.
Chryse-Xanthe: Whitish to the OAA observers from about CML 50 deg. in the
afternoon. Also seen light at the a.m. limb, but no brighter than other
equatorial deserts at local noon.
Libya: The OAA recorded "morning mist following Libya" under CML 265 deg. on
Dec 9. Gray must have had a similar experience on Dec 23 when he found the
Syrtis Major apparently slightly veiled when rising, under CML 233 deg. It was
not seen to be light near the CM.
Elysium: Light at the evening terminator, the a.m. terminator and lightish in
the afternoon, but never really bright.
Tharsis; Nix Olympica; Alba: On Dec 2 under CML 149 deg. Gray sketched a mass
of extensive bright cloud over the evening (p.) terminator, from which Nix
Olympica (the orographic cloud over the slopes of Olympus Mons) was but
imperfectly resolved. Alba was light but not easy to the same observer at the
terminator on the same date.
Aeria: Some indications of both morning and evening cloud.
Tempe: No reports of cloud activity here as yet.
Noachis: Masatsugu Minami, Nov 25, 28, found it whitish on the evening
terminator (20-cm OG).
S. polar hood: A constant feature, but variable both diurnally and with
longitude. Thus: Minami and Takashi Nakajima (OAA), Nov 23, S. limb hazy and
light, especially on the morning side (CML about 50 deg.); Gray Nov 6 (CML 27
deg.) p. side of hood brighter than the following in W58 green.
Dark markings
The following comments by Martin Gaskell (20-cm refl., Dec 8, CML = 175 deg.)
should encourage other Section members to start their observations: "The
northern maria around the NPC (Scandia-Panchaia) were the darkest features
visible. The diffuse dark markings in the Diacria-Propontis-Phlegra region
were surprisingly dark in white light given that the disk was only 5.4
arcseconds across." No changes in the markings from 1997 have yet been
detected, but increasingly fine surface details are being recognised. Thus
David Gray did well to make out the little N-S elongated "oasis" of Nodus
Alcyonius Np. the Syrtis Major. On Nov 23 Minami, with Nakajima, was even able
to detect colourations with a 20-cm OG. M.Acidalium was slightly dark brownish
and the Aurorae Sinus region dark bluish.
On this last point of colour, the Director wonders if the difference in colour
between such markings at aphelic apparitions can be ascribed to the presence
of the bluish-white equatorial cloud bands? Such bands would tend to make the
Aurorae Sinus, Syrtis Major, etc., more bluish than far northern areas such as
Utopia and Mare Acidalium, even though the bands are rarely visible through
direct observation near the CM with small telescopes. If this explanation is
correct (rather than there being real differences in the hues of the dark
markings themselves), then we can deduce that the ECB were present in many
past apparitions even if they were not reported as such (e.g., 1935, 1952,
and through to the present time). It will be easy to search the literature for
earlier examples, though these are the earliest I can think of offhand where
there were significant tonal differences in the manner described.
From the bookshelf
"Patrick Moore on Mars" is the title of a popular new Mars book by Patrick,
his first for two decades. It is published by Cassell (1998), and it is
recommended to members as an excellent guide to the Red Planet. Patrick is
unique in having contributed observations to the Mars Section at every
apparition from 1948 to the present.
Iakovos Stellas writes from Athens that he has completed the draft of a
translation of E.M.Antoniadi's book, 'The Planet Mars' from English into
Greek. He hopes to have discussions with publishers about the chance of
printing an edition in Antoniadi's native language, which would be very nice.
In the 1970s Patrick Moore translated the original French edition of 1930 into
English.
I am often asked if this English edition is still available, and always have
to say that it has been out of print for some years. If any member comes
across secondhand editions of this, or any other classic Mars books, and does
not want them for him or herself, please let me know as I may be able to match
people with books. For myself I would like to find the French edition of
Schroeter's Mars book: I have it in German but cannot easily read it! I would
also be interested in getting copies of the Annals of the Lowell Observatory,
the formal reports on Mars by Lowell and his assistants covering the years
1894 to 1903 (volumes 1-3).
Reporting data to the Section
Send mail to Cherry Tree Cottage, 16 Upper Main Street, Upper Benefield,
Peterborough PE8 5AN, Great Britain; home telephone 01832-205387; home email
Rmckim5374@aol.com. (Do not use the former email address for my place of work
(mckim@oundle.northants.sch.uk).)
Richard McKim, Director, 1999 January 7
Back to Date Menu
November, 1998
British Astronomical Association
Mars Section Circular 1998-99, No. 1
General
Mars is still very far from opposition, but the writer knows of observations
as early as August 19. Six observers have reported their work, and this
Circular describes some details seen from then until November 15 (Ls = 7-57
deg., D = 3.8-4.9 arcsec). Some notes about what to look for during the
present apparition were published in the BAA Journal, 108 (5), 243-245 (1998).
Although the planet is steadily drawing closer, its N. declination is
decreasing, and will become S. of the celestial equator in early December.
North polar region
With these early observations, on occasion no dark markings can be seen on the
tiny disk, due to lack of resolution rather than dust storm activity. Even
then, sketches that just portray the NPC accurately will be useful. Drawings
may be made every 15 or 20 minutes. Remember to estimate the cap in tenths of
the planet's diameter when transfering the mental impression to a Section
report form.
Observations did not begin early enough this year to document the transition
from polar hood to cap. Sketches do show the decline in size of the NPC,
though no fine details could be expected. A dark collar was seen by Nicolas
Biver on September 20, 26, by Richard Schmude on September 27, by David Gray
in October and by Mario Frassati on October 28. Drawings by Martin Gaskell
during October 12-13 (Ls = 42-43 deg.) place the NPC S. edge at latitude= 70-72
deg., and two by Gray on October 31 (Ls = 50 deg.) gave 74-75 deg. These
results are very close to the BAA data for the earlier apparitions of the
1990s (and 80s). More measures please!
Atmospheric activity
Elysium: Gray reported slight whiteness here with the region near the CM,
October 18, 19, and more so with the region on the morning side, October 22,
23, whilst Biver's sketch of September 26 shows it light at the morning limb.
(As Gray remarks, Elysium is sometimes detected not by its intrinsic
brightness, but by the duskiness of its surroundings. Would observers
therefore be explicit in their descriptions, please!)
Nix Olympica: detected as a light spot by Gray on the afternoon side on
October 23.
Tharsis: On October 30 and 31 Gray reported a striking, large bright tongue
of cloud, visible in white light and in W15 yellow, stretching from W.
Tithonius Lacus (the latter feature, a dusky triangle, was near the CM, at CM
long. 73 to 80 deg.), broadening towards the morning limb. Terrestrial cloud
prevented a view in red or blue light. This seems to have been white morning
cloud over Tharsis. The Director recalls a roughly similar view in February
1995, at a very slightly later seasonal date, so it may be a seasonal type of
cloud. There is no real evidence for it having been a dust storm.
Chryse-Xanthe: bright on the evening terminator.
Hellas: Under CML 254 deg. on September 20, Biver (10-inch refl.) did not draw
it light. More data are needed for this region of the planet.
The October work by Frassati and Gray reveals S. limb haze at all longitudes,
sometimes very striking. A report by the OAA (Japan), October 2-9, confirms
this.
Dark markings
These seem normal, like 1995 and 97. Using his 14-inch Dall-Kirkham Cass.,
Gray has already made detailed sketches showing such small details as Idaeus
and Achilles Fons on the Nilokeras streak. Solis Lacus remains large, as in
all the apparitions from 1984 through 1997. The Propontis area was dark (at
lo-res), as were the S. maria, Syrtis Major, Mare Adidalium, etc. The SE dark
border to Elysium (Trivium Charontis-Cerberus) remains invisible or virtually
so.
Reporting data to the Section
Please note that since the last apparition I have moved house, and am now
living at this address: Cherry Tree Cottage, 16 Upper Main Street, Upper
Benefield, Peterborough PE8 5AN; home telephone 01832-205387; office fax and
answering machine 01832-274052; home email Rmckim5374@aol.com. (Do not use the
former email number for my place of work (mckim@oundle.northants.sch.uk).)
Richard McKim, Director, 1998 November 20
Back to Date Menu
June 1-15, 1997
From mckim@oundle.northants.sch.uk Tue Jun 24 09:15:35 1997
Mars, 1996-97: British Astronomical Association:
Twelfth Report on observations 1997 June 1-15
General
D: 9".0 to 8".2, Ls: 126 to 133 deg. UK weather and seeing conditions
remained fairly good, but several observers have ceased observing on
account of the diminutive disk. No changes in surface features have been
noticed. The summer NPC remains static and clearly defined. There has been
no indication of atmospheric dust activity. Selected observations are set
out chronologically; this report will be very incomplete in longitudinal
coverage but is released now on account of its topicality.
Selected observations
June 1 Meredith CML 312 deg: Hellas bright on p.m. side.
June 4 Teichert CML 275 deg: Hellas and (p.m.) Elysium light. Observer
found Mare Hadriacum very dark.
June 4 McKim CML 287-292 deg: Hellas bright. Syrtis Major is fainter than
the very dark M.Tyrrhenum. Hellas and (p.m.) Elysium bright.
June 7 Gaskell CML 353 deg: Evening cloud over Libya. A band (of light
evening cloud?) the width of Hellas ran northwards from Hellas over
Iapigia towards Deltoton; it was of similar brightness to Deucalionis
Regio.
June 8 Meredith CML 247 deg: normal albedo features.
June 14 Schmude CML 263-272 deg: Syrtis Major weak (51-cm refl., x570);
suggests light a.m. haze, similar to diurnal effects seen in May. Also NPR
"dull white", and clouds at Np limb and Nf terminator.
Richard McKim, Director
1997 June 24th
fax and answerphone 01832-274052; home telephone 01832-274553
email address mckim@oundle.northants.sch.uk
To email recipients ONLY:
I will not have the use of this email terminal except on rare occasions
during the School summer holidays, June 27 to August 29, approx., although
it may be possible to SEND one more email circular in early July.
Therefore please DO NOT SEND ME EMAIL during this period as it tends to
build up and cause the whole system to crash as it is shared by some 100
other users (in which case your message will be lost). But you can phone,
write or fax me. If you have not yet done so, please mail me hardcopies of
your observations (visual) a.s.a.p., together with any overall impressions
you may have of the apparition (which may be quotable in any later
report!). As this is more or less the end of the apparition, let me thank
you for your communications, and let us all hope that the NASA Mars probes
will be really successful. Watch the press this summer!
Back to Date Menu
May 1-31, 1997
From mckim@oundle.northants.sch.uk Mon Jun 2 10:58:32 1997
Mars 1996-97: British Astronomical Association
Eleventh Report on observations 1997 May 1-31
General
-------
Between May 1 and May 31, Ls increased from 111 to 126 deg., whilst the
apparent diameter shrank from 11.5 to 9.0. Mars Pathfinder is still
functioning well, and camera tests have been carried out. Larger
meteorological and albedo features should remain observable given good seeing.
New contributors included John Rogers (UK), Frank Melillo (USA) and Sam Whitby
(USA). A Mars Telescopic Workshop (the second of its kind) is planned for
October 2-3 in the Tucson mountain foothills, in order to define the state of
the martian atmosphere and surface just prior to the Pathfinder landing, and
to compare the atmospheric activity in 1997 with recent apparitions. The
Director has details for anyone interested in attending.
More HST images
---------------
The HST images described in issue no. 10 will feature in the August number of
the Journal. Further HST images were acquired on March 20 but not released
until May 20. One with CM long. 94 deg. (not reproduced here) shows Acidalium-
Hyperboreus, several volcanic calderas, the complex Valles Marineris area and
Solis Lacus. The Solis Lacus is still conspicuous but it is clear that the
north-western (e.g., Nf.) part has faded, becoming overlaid with dust. The
Phasis area has also faded out. Thus the whole region has returned to
something more like its classical appearance, in contrast to the long sequence
of changes from 1973 to the present. Greatly foreshortened this year, it has
only been well-resolved in the HST images. A blue-light image (same CML) shows
Tempe-Arcadia dark, confirming the telescopic impression of a rather strong
reddish colour thereabouts. There was no polar haze. Next HST images are due
on June 4 , and June 26-29.
Back to the BAA observations covering May 1-31:
North polar region
------------------
The NPC summer remnant appears static; Hyperboreus Lacus was still easy to see
at the close of the month. Olympia was still reported by the OAA (Japan) in
early May. There was still no real sign of polar haze.
Surface features
----------------
Alan Heath's April drawings showed the Lunae Lacus large and diffuse; the
Director had described it as conspicuous in a previous Circular, meaning large
rather than dark. Several observers with relatively small apertures have seen
the martian volcanoes as albedo features: they are also shown on the newly
released Hubble image described above. For instance, Michael Hendrie on May 14
saw Ascraeus Mons as a diffuse dusky smudge (15-cm OG, x330), as did several
others. Cave on May 9 saw Nodus Alcyonius tapering to the south.
Dust storms (yellow clouds)
---------------------------
Nothing positive to report again.
White clouds
------------
Throughout May, the Tharsis and Nix Olympica orographic clouds remained
visible. However, the preceeding limb no longer corresponds with the sunset
terminator, and so (since April) the most favourable conditions for viewing
the clouds under evening illumination have passed. Elysium appeared lightish
near the disk centre and brighter at the limb or terminator. Some observers
were lucky enough to see the small Elysium Montes cloud (e.g., Arthur Bowyer
(30-cm refl.) on May 1, under CML = 242 deg.). Hellas remained bright
throughout the martian day. Eridania, Ausonia and Argyre were also light.
Libya-Isidis-Aeria and Chryse-Xanthe exhibited diurnal cloud activity, as did
Tempe. The Libya-Isidis-Aeria cloud caused Syrtis Major to appear faint in
whole or in part at the limb or terminator during May (and April).
Richard McKim, Director
1997 June 2nd
fax and answerphone 01832-274052; home telephone 01832-274553
email address: mckim@oundle.northants.sch.uk
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April 16-30, 1997
From mckim@oundle.northants.sch.uk Sat May 10 07:07:17 1997
Mars, 1996-97: British Astronomical Association:
Tenth Report on observations 1997 April 16-30
General
D:12".9 to 11".5, Ls: 105 to 111 deg. UK weather and seeing conditions
were a little less satisfactory than in the first half of the month, but
many observations came to hand. Vanessa Cave (USA), David Graham (UK),
Terry Platt (UK) and Antoine Van de Jeugt (Belgium) sent in their first
contributions of the apparition. Congratulations to Section member Dr
Patrick Moore on the 40th Anniversary of his 'Sky at Night' TV programme.
Earlier still, fifty years ago, at the 1947-48 apparition, Patrick made
his first contributions to the Mars Section, then directed by P.M.Ryves.
And he has sent in observations at every apparition since! Meanwhile,
NASA's Mars Pathfinder is still on course for a July 4 landing.
Special comments upon the new HST images
As recommended in a recent Circular the Director has studied the three
'colour' WFPC images released onto the Internet. All were taken on March
10, and released on March 20. There are other images too, filter versions,
but I will just discuss the colour set here, all of which have incredible,
diffraction-limited resolution (one pixel =3D 22 km on Mars!). Each colour
image combines blue (433 nm), green (544 nm) and red (763 nm) filter
images. The accompanying Press Release from the Space Telescope Institute
states that a preliminary analysis reveals some dust as well as water ice
crystal clouds over Terra Tyrrhena [Mare Tyrrhenum], Noachis Terra
[Noachis] and Hellas, as well as Vastitas Borealis. However, inspection of
the colour images shows little evidence of airborne dust.
(A) CML =3D 160 deg. Olympus Mons is just E. of the CM, its caldera marked
by thin white clouds and the usual orographic cloud streaming over its
western slopes in a NW direction. Remarkable detail is seen in the evening
Tharsis orographic clouds which cover a good part of the E. limb. Euxinus
Lacus is very small on the CM. NPC outliers are seen in several places. To
the far south, Caralis Fons is clearly seen poleward of Mare Sirenum; the
NW end of the latter Mare remains obscure (since 1986, now).
(B) CML =3D 210 deg. Elysium straddles the CM. The extraordinary pallor of
Trivium Charontis and Cerberus (I) is noticeable at once. Has the region
faded even further than in 1995? Trivium Charontis comprises a few tiny,
complex spots on my monitor screen, whilst Cerberus is invisible apart
from a tiny dark spot. Many observers have missed these features
completely this apparition (and last). Interesting that Elysium does not
appear on 19th Century sketches before the 1830s and 40s, when observers
such as Galle, Beer and Maedler drew it. Neither Herschel nor Schroeter,
nor any of their predecessors ever unambiguously figured it. It seems that
the area is now a site for dust deposition, and is enjoying a period of
obscurity! Had Cerberus-Trivium Charontis ever previously been as dark and
as intense as it was in the first decade of the present century, it would
have surely been recorded even in the 1700s. Thus perhaps the desposition
of dust there marks a return to the circulatory regimes that existed then,
when no evidence was found for large dust storms. On this HST image, the
other points of interest are the dark, comma-shaped Propontis I, looking
as it did in 1993-95, and the widespread shading between the lightish
Elysium and Propontis I, which is all that remains of Phlegra-Styx, the
classical E. border of Elysium. Note also the bright orographic cloud over
Elysium Montes near the CM, and the irregularities in Mare Cimmerium that
closely resemble the spoch 1988-95. Olympia is foreshortened near the CM,
and the polar ices are highly irregular.
(C) CML =3D 305 deg., with the following edge of Syrtis Major central.
Hellas is bright, bluish-white, presumably frosted over, but also shows a
dusky E-W streak dividing the equally bright N. and S. halves. The detail
in the Syrtis includes the Huygens crater complex, and intricate
irregularities on all sides. Moeris Lacus seems unchanged since 1990.
Further north, the Nodus Alcyonius is a dark, elongated streak, but
contrary to the impression I reported from contemporary CCD images in a
recent Mars Section Circular, it is not connected to Casius/Utopia.
Nilosyrtis is a faint chain of small irregular spots, Boreosyrtis is
complex and remarkably like its aspect in 1990-95 (and in the USGS
albedo-topographic charts), whilst Nepenthes remains absolutely invisible.
The E. end of Sinus Sabaeus is pale, but reaches Iapigia. Edom crater is
visible, but not light on the morning side, while bright white evening
cloud covers Elysium. Aethiopis-Isidis shows very thin diffuse white cloud
seeming to merge with the limb haze on the E. side. The Deuteronilus seems
less well-marked than it appears in the ground-based visual and CCD work.
The NPC dark collar is some way south of the summer residual frost; this
may well have some bearing upon past ground-based measures of the summer
cap. The NPC summer remnant is complex, with the broad Chasma Boreale
cutting largely across the cap from the longitude of Mare Acidalium.
Olympia appears as a pale, irregular cap outlier, rather reduced in size.
Back to the latest April 16-30 observations:
North polar region
The NPC summer remnant looks static now. Olympia was seen by Cave on April
16, when it was drawn rather small by him. Both Cave and Teichert on April
30 and 13-17 respectively saw a tiny white remnant near long. 10 or 20
deg. (March drawings just to hand from Niechoy also show some NPC
outliers, and both he and Graham found Ortygia rather bright on March 7
and 10, respectively.) Some observers report seeing the NPC surrounded by
a lightish region.
Surface features
Gaskell confirmed the Director's view of the apparently more conspicuous
Lunae Lacus (Circular No. 9). A pity the region has not been imaged by the
HST recently. Gaskell also commented upon the rich red colours visible in
the Arcadia region when observing with a friend's 51-cm reflector. Cave
continued to see Juventae Fons as very tiny and dark in excellent seeing.
Tanga on April 13 (42-cm OG, Turin observatory) was fortunate to see
"three tiny (but incredibly dark) dots corresponding to Ascraeus, Pavonis
and Arsia [Mons] (the last one on the [following] limb)." This calls to
mind one of the 1995 HST images where one of the summits of the volcanoes
poked through morning haze. The Director was lucky to see a similar
instance of this phenomenon in the 1995 apparition, but he did not catch
it in 1997.
Dust storms (yellow clouds)
Nothing positive to report.
White clouds
(An incomplete report!) The Tharsis and Nix Olympica orographic clouds
remained visible. The ALPO (Martian Chronicle, 1997 April edition) found
the Olympus Mons orographic cloud less prominent, only visible through the
W47 filter (blue-violet light). Southern limb haze was noticeable. Hellas
has been bright throughout the martian day: frosted floor now? Patrick
Moore, April 24, found Hellas as bright as he had ever seen it, and
brighter than the NPC. Teichert also found Hellas brighter than the NPC in
green, blue and red light. On April 29 the Director followed Hellas as it
appeared on the morning side. The S. limb was whitish under CML =3D 252
deg., as observations began; under CML 268 deg. Hellas was differentiated
from the general S. limb whiteness as a very bright patch. Eridania,
Ausonia and Argyre were light. Knott on April 20 drew Edom lightish in
blue (but not in white) light when somewhat W. of the CM. Elysium and
Tempe appeared lightish near the disk centre and brighter at the limb or
terminator. Libya-Isidis and Chryse-Xanthe are similar. No reports of the
'Blue Clearing' have been received, all W47 filter observations being
negative.
Richard McKim, Director
1997 May 10th
fax and answerphone 01832-274052; home telephone 01832-274553
email address mckim@oundle.northants.sch.uk
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April 1-15, 1997
From mckim@oundle.northants.sch.uk Thu Apr 24 12:46:22 1997
Mars, 1996-97: British Astronomical Association:
Ninth Report on observations 1997 April 1-15
General
D: 13".9 to 12".9, Ls: 98 to 105 deg. UK weather and seeing conditions
remained good.
North polar region
Again, no N. polar haze was evident in white ight. The NPC seemed to have
reached its minimum size, but measurements will be needed to confirm this.
Hyperboreus Lacus was still conspicuous, and Olympia showed up on Dijon's
CCD work and to Shirreff (Apr 7) visually, on the morning side.
Surface features
Much fine structure was again seen. Observers paid attention to the fine
detail around Mare Acidalium, e.g., Hendrie on Apr 12 (15-cm OG)
accurately portrayed Acidalium's dark NW tail, Tanais, together with the
dusky Baltia. On Apr 15 the Director found Lunae Lacus rather large, and
apparently darker than before: he felt the region to be a little different
to its earlier appearance visually and upon the HST images. Observations,
please! In 1982 Lunae Lacus and Uranius darkened at the time of a dust storm
in Tempe-Arcadia.
Dust storms (yellow clouds)
There is nothing positive to report, but see the note on Lunae L. above.
Dr Ebisawa (49-cm refl., Tokyo, Japan) has sent details of his work thus
far. Of special interest, on 1996 September 18, CML = 154 deg., Ebisawa
sketched a small southward inflexion in the NPC's contour; he notes that
this corresponds to the place of the dust storm imaged by the HST (see
earlier Circulars).
White clouds
Dijon's images (reproduced in the paper edition of this Circular) were
among the many received that showed the complex spotty pattern of evening
white clouds over Tharsis-Amazonis-Arcadia. Nix Olympia exhibited white
morning cloud, became less easy to see by local noon, then gradually
brightened towards evening. Several observers including the Director drew
attention to the large white morning cloud over Tharsis and E. Memnonia -
E. Amazonis, visible when Mare Acidalium was on or somewhat p. the CM.
S.Moore (22-cm refl.) on April 15 reported a small bright white cloud in
S. Tempe (seen in blue, invisible in red light), but the Director
contemporaneously saw only a general lightness in Tempe. The region showed
bright a.m. and p.m. clouds but was less conspicuous about mid-disk.
Elysium was bright on the morning terminator, Cebrenia being included or
brightening separately. Near the CM and in the afternoon, no more than a
small light cloud was seen over Elysium Mons, or a slight lightness over
Elysium generally. In the evening Elysium was wholly or partly brightened
by white cloud. Siegel on Apr 6, under CML = 100 deg., reported that an
equatorial cloud band was faintly visible in W47 and 80A, and very faintly
visible in W58 and integrated light. Other observations of the phenomenon
were reported by Troiani. Some observations of the 'Blue Clearing' were
again made.
Richard McKim, Director
1997 April 25th
fax and answerphone 01832-274052; home telephone 01832-274553
email address mckim@oundle.northants.sch.uk
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March 16-31, 1997
From mckim@oundle.northants.sch.uk Wed Apr 23 10:46:17 1997
Mars,1996-97: British Astronomical Association:
Eighth Report on observations 1997 March 16-31
Personal:
The writer is very sorry to have to report the death of Dr Leonard Martin
in early April. Leonard made some outstanding analyses of the great dust
storms of the 1970s in a long professional career at the Lowell Observatory.
He had retired only recently. The Director met him at Flagstaff in 1994, and
was given every assistance with regard to the Observatory's archives. On
several occasions Leonard gave valuable advice to both the BAA and ALPO.
General:
D: 14".1 to 13".9 (14".2 at opposition on Mar 17; closest approach Mar 20),
Ls: 91 to 98 deg. New contributors were Arthur Bowyer, Andrew Farr, Alan
Heath, Michael Hendrie, Lee Macdonald, Dr Patrick Moore, Dr Stewart Moore,
David Strange and Peter Wade in the UK, Emilio Colombo in Italy and Gerard
Teichert in Frnce. Thanks also to Wolfgang Meyer for German Mars observations.
UK weather and seeing conditions were often good. Check out the incredible new
HST images on the WWW if you can, at:
http://oposite.stsci.edu/pubinfo/PR/97/09.html
North polar region:
No N. polar haze was evident in white light. Schmude on Mar 27 found a small
detached part of the cap near long. 340 deg (probably the same feature
observed by Devadas on Mar 7). Olympia was well shown in the CCD work by Dijon
and Strange, and visually by Fisher and McKim. Hyperboreus Lacus was widely
observed, and from it extended a thin dark fringe to the NPC covering a wide
range in longitude. Warell reported a difficult, N-S rift in the cap on Mar 23
(CML 244 deg., 16-cm OG) and 24 (CML 246 deg., 36-cm OG).
Surface features:
Much fine detail has been drawn and imaged, despite the small size of the disk
at opposition. In excellent seeing Cave could see Juventae Fons. The southern
regions were still foreshortened but Solis Lacus clearly remains large and
dark; no internal details have been detected. No-one has reported Phasis this
apparition, but it is a delicate feature even when the presentation is
favourable. Likewise Gallinaria Silva, the 'oasis' at the N. end of the
latter; this has probably faded. The Melas Lacus-Tithonius Lacus complex is
rather dark. The OAA drew attention to the lack of redness in Thaumasia
compared with Daedalia-Memnonia-Amazonis. CCD work by Strnage and visual work
by Warell suggests that the Nodus Alcyonius is faintly joined to S. Utopia by
a half-tone shading; this area also darkened between 1982 and 1984, before
fading again.
Dust storms (yellow clouds):
There is nothing positive to report.
White clouds:
(A few interesting points, not a complete account; w.c. activity remained
high.) Small white clouds were seen on the borders of Nilokeras by Cave
on Mar 19 (between Niliacus L. and Achillis F.) and 21 (W. Tempe). Tempe was
generally not very bright near mid-disk but was light in the morning and
evening. Hellas remained very bright, especially in its NW (Nf.) corner. A
large cloud habitually covered Libya-Isidis R. on the morning terminator.
A wide general 'Blue Clearing' is apparent from several observers' work.
Richard McKim, Director
1997 April 19th
fax and answerphone 01832-274052; home telephone 01832-274553
email address mckim@oundle.northants.sch.uk
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March 1-15, 1997
Mars, 1996-97: British Astronomical Association:
Seventh Report on observations 1997 March 1-15
General
-------
D:13".2 to 14".1. UK weather improved. Jean Dijon joined the BAA team.
North Polar region
------------------
No N. polar haze was evident (Int. light). Hyperboreus Lacus, Rima
Borealis and Olympia were still visible.
Surface features
----------------
As earlier. The disk has now reached maximum diameter, so please observe
intensively over the next few weeks. The Director could glimpse the complex
mottled structure of Mare Acidalium in fine seeing; the Mare seemed darkest
on the Nf. side. Niliacus Lacus was large and Achillis Pons obvious. Fine
details in the nearby deserts were also caught, such as a half-tone shading
marking the S. part of classical Gehon. To the north, Iaxartes connected
Mare Acidalium to Hyperboreus Lacus.
Dust storms (yellow clouds) and White clouds
--------------------------------------------
Re. the possible dust storm over Tempe alluded to in Circular No. 6, Jim Bell
informs me that this was suspected by Dr Leonard Martin on Feb 14 and 15.
However, IRTF data on Feb 16 and 17 show no dust. Tempe has not been
especially light on the morning side, but Devadas found a bright afternoon
cloud over Tempe on Mar 2 (under CM 86 deg.) as well as a small, bright cloud
over Alba on the a.m. side. None of the BAA observers reported dust in Tempe
in February or March.
White cloud activity is now quite marked. The areas described in the
last report remained active, with Chryse and Xanthe both exhibiting a.m. and
p.m. cloud. On Mar 3 Knott (22-cm refl., CML 61 deg.) saw a very bright
discrete white patch on the a.m. limb over Olympus Mons, visible in blue, but
not in red light. The orographic clouds over the Tharsis volcanoes and
Olympus Mons continued to show up clearly on the evening side. The Director
on Mar 10 and 11 saw Argyre (I) whitish on the morning limb (surface
frost?), with white cloud over Tharsis-Ophir-Candor: the latter
white cloud extended further onto the disk by running along the S. part of
classical Xanthe. Indeed, white cloud upon mid-disk tended to extend
east-west along the equatorial border of Sinus Sabaeus (with Edom
sometimes separately bright). A number of reports of the 'equatorial cloud
bands' (ECB) have ben received. Thus with Syrtis Major near the evening
terminator, evening cloud over Aeria has been thought by some observers to
be thinly connected to morning cloud over Chryse/Xanthe by a bright E-W
streak approximately along the martian equator. However, some such
observations are simple optical illusions. The Director on Mar 10 and 11
under CML circa 20 deg. did not see ECB connecting the morning and evening
bright patches. Objective wispy ECB clouds were imaged by the HST in 1995,
and by visual observers for many years previously. Most recently Troiani
on Mar 12, CML 65 deg., reported an ECB connecting evening cloud with morning
cloud over Memnonia and Tharsis. Southern limb haze was also present. Troiani
remarked that a large number of thin white clouds were partly veiling the albedo
features. HST images in 1995 showed wisps of white cloud crossing M.Acidalium
and thus reducing its intensity. The foreshortened Mare Sirenum may be
affected by the haze present along the S. limb at some CML.
Future European Missions to Mars
--------------------------------
ESA publication D/SCI/96(2), Intermarsnet: Report on the Phase A Study,
considers the scientific benefits of a network of martian groundstations. The
study is based upon the 2003 launch windows for the ESA M3 opportunity; the
idea is to place three groundstations in a triangle of side 1000 km.
Proposed sites are: A; Gusev crater [in classical S. Zephyria] at lat. -15 deg.,
long. 184.5 deg., alt. 0 km; site B: Uranius Patera plains at +29 deg., 93.5
deg., alt. +1 km; site C: Coprates highlands [S. Xanthe] at -2 deg., 49.5 deg.,
alt. + 2 km.
Emailing the Director
---------------------
My email facility will not be accessible to me during Mar 22 - Apr 17. Fax,
write or phone!
Richard McKim, Director
1997 March 19th fax and answerphone 01832-274052; home telephone
01832-274553
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February 16-28, 1997
Mars,1996-97: British Astronomical Association:
Sixth Report on observations 1997 February 16-28
General
-------
The disk diameter increased from 12.0 to 13.2 arcseconds. New contributors
were Mrs Elisabeth Siegel (Denmark), Mrs Komala Murugesh (India), Giovanni
Quarra and his colleagues (Italy), and David Fisher and John Knott in the UK.
Extremely bad weather conditions prevailed in the UK. Circulars No. 4 onward
appear on the new BAA Mars Section Web page, courtesy Jim Bell of MarsWatch
(http://marswatch.tn.cornell.edu/baa.html), and are emailed to those able to
receive them. Other observers receive them by post when the Director
acknowledges observations. Observers should check the Web site
http://marswatch.tn.cornell.edu/irtf.html for remarkable current hi-res IRTF images
by Bell and colleagues. Section members are now showing more detail in their
drawings. Devadas has supplied the largest number of observations so far, and
special credit must go to Quarra and colleagues for superb CCD work at five
wavelengths from the ultrraviolet to the infrared; examples are attached
[paper copies of this Circular only].
North Polar Region
------------------
The North Polar Cap was quite small, about 20 degrees across. Devadas made
out the bright detached outlier Olympia. Warell reports clear skies from La
Palma on Feb 22-23 and the observation of a rift in the cap around long.180
deg (the p. end of Rima Borealis?). Hyperboreus Lacus continued to be
prominent, marking the only remaining really dark part of the NPC border. No
sign of polar haze was detected in white light, though images by Quarra et al.
, on Feb 8 and 9 in UV (330 nm) and B (420 nm) showed haze over the cap. In
1982 the BAA Mars Section found the onset of the polar hood about Ls = 152
degrees, and at 161 degrees in 1984. (Ls is 92 degrees at opposition on Mar
17.) Observers should pay special attention to this region. The Section
received an email alert from M.Murakami of the OAA that under CML = 194-204
deg. on Feb 10 (Ls = 76 deg.), Minami and Nakajima found the following quarter
of the cap more dull and yellow than the rest. Seeing was good. On the same
date from the UK under CML = 270 deg., Shirreff (25-cm OG, poor seeing) found
nothing odd about the cap, and Cave (Long Beach, USA, 32-cm refl., x660) on
Feb 10-16 under CML = 323-26 deg., in very fine seeing found the cap uniformly
sharp and bright, with a notch in the longitude of M.Acidalium (long. approx.
30 deg.). Quarra's multi-filter images (Feb 8-9, CML approx. 280-3550 deg.)
showed Olympia well, but no tonal differences. Later BAA observations under
the same CM longitudes viewed from Japan were all negative. More details of
the Japanese observations were given in the OAA's CMO No. 185: red light CCD
work on Feb 8 apparently also showeds the effect under CML = 191-200 degrees.
Surface features
----------------
The HST images are available on the MarsWatch Web site. The Director has
studied these closely. The images of Mare Acidalium in December are almost
indistinguishable from those in 1995. No largescale dust activity can have
occurred since then, despite a report from Todd Clancy back in 1995 December
which suggested that dust was then widespread as indicated by CO microwave
observations. A copy of the BAA 1992-93 apparition map is attached to this
Circular together with a printout from the Web of the long. 45 deg. image
cited above [paper copies only]: the close resemblance between these
apparitions will be at once apparent, so there is little need for a further
description here except to add that the far northern regions can be better
observed this year. Note that Pandorae Fretum remains dark.
Dust storms (yellow clouds) and White clouds
--------------------------------------------
Jim Bell emailed the Director to draw attention to a fine NASA IRTF image from
Hawaii now posted on the Internet. This was secured by Bell and others on Feb
17.Tempe appears normal in the near-IR at 2.331 microns (CML = 43 deg.),
though Bell suggested that Dr L.J.Martin (Lowell Observatory) had recently
seen a possible brief dust event there a few days earlier: more details have
been requested by the Director.
Xanthe remained rather bright both at the evening terminator and on the
morning limb; clasical Chryse less so. It seems that the martian sky is clear
over the Pathfinder landing site. Tharsis, Thaumasia and Sinai (IAU) have all
appeared bright on the morning limb, and the Tharsis orographics were most
prominent near the evening terminator. HST pictures show the clouds'
appearances varied on a minute scale between images during September to
January. Aeria and Tempe have exhibited diurnal cloud, too.
Elysium has shown up bright in whole or in part on the evening side as
well as when rising. Hellas was dull white to Sturdy under CML = 268 deg. on
Feb 15. Hellas was bright on mid-disk to Schmude on Feb 23; he could glimpse
Hellas through the W47 (blue-violet) filter, but no albedo markings were seen.
Schmude found Hellas especially bright (at most visible wavelengths) when it
was on the morning limb. Siegel (20-cm SCT) on Feb 2 under CML = 6 deg. also
estimated the Blue Clearing as 0. Quarra's images (Feb 9) showed a UV/violet
cloud over the location of Syrtis Major that rotated with the planet. Dark
markings in violet light did not correspond with albedo features. Would
observers please comment on the 'BC' effect? I have had few remarks about it
so far.
Richard McKim, Director
1997 March 12th
NEW email address mckim@oundle.northants.sch.uk
fax and answerphone 01832-274052; home telephone 01832-274553
Back to Date Menu
February 1-15, 1997
From mckim@oundle.northants.sch.uk Mon Feb 17 13:48:40 1997
Mars, 1996-97: British Astronomical Association:
Fifth Report on observations 1997 February 1-15
General:
The disk diameter increased from 10".6 to 12".0. New contributors were Mrs
Sally Beaumont, David Storey and K.M.Sturdy (UK), and ALPO Mars Coordinator
Carlos Hernandez (USA). No attempt has been made to analyse all the
observations submitted, some of which relate to earlier months (!).
North polar region:
The North Poalr Cap retains its dark collar but is shrinking appreciably all
the time. There are indications thgat it is slightly asymmetric about the
rotational pole. Schmude (15-cm refl.) found the cap rather dull under CML
185 deg. on Feb 1, but Warell under CML = 71 deg. on the same night found it
bright. Hyperboreus Lacus is now visible near the NPC; Ishadoh (OAA, Jan 31)
reported the observation of Olympia.
Surface features:
Devadas (36-cm refl.) found Meridiani Sinus well marked, but the prongs of
Dawes' Forked Bay were not well separated, the region between them being
shaded. Both Devadas and the Director could see the streak of Deuteronilus
well-marked to the north. On Feb 8 the Director found the E. end of Sinus
Sabaeus just as it appeared in 1995, with Deltoton Sinus still faded.
Nepenthes was invisible. Warell saw Ganges dusky, but paler than Nilokeras.
Achillis Pons is a half-tone. Solis Lacus is dark, as are Melas Lacus and
Oxia Palus.
Dust storms (yellow clouds):
In an email dated Feb 11, Jim Bell, MarsWatch Coordinator notes that "dust
activity is remaining rather minimal" and goes on to write that as the
American probes get closer to their encounter dates, NASA "will be getting
more and more nervous about dust opacity, as this will affect the entry and
operations of Pathfinder an the aerobraking manoeuver of Global Surveyor."
In CMO 184 M.Minami (OAA) queries the source of my statement in BAA Mars
Circular No. 2 that Parker imaged the September 18 dust storm. I quote from an
emailed November ALPO Mars Circular (which had also been sent to the OAA): "On
Sept. 18, 1996, Don Parker, with help from Carlos Hernandez, imaged a dust
storm that was associated with the NPC." In the same CMO it is reported that
G.Quarra et al. (30-cm Cass.) obtained infrared CCD images showing that NW
Elysium apparently contained a small dusty patch on Jan 17. BAA visual data
for mid-January do not show this brighter area at lower resolution. Hernandez
emailed the Director to report a suspected dust storm in Thaumasia on Jan 29
under CML = 132 deg: Solis L. was seen to be surrounded by a bright region in
red, but not in blue light. However, no obscuration was shown on his drawings,
and the region was adjacent to very bright S. limb haze. CCD images by Parker
on Jan 29 and Quarra on Jan 31 showed no dust activity, whilst BAA visual
observations by Devadas, Gray, Storey and Sturdy (Jan 20-26) show only white
morning and evening cloud over Thaumasia, so it must be concluded that there
was no storm. The brightness of Thaumasia at this season is typical: see the
1980 and 1982 BAA Mars Reports.
White clouds:
The morning limb showed more diurnal cloud than the evening terminator. The
Director on Feb 8 (22-cm refl., CML = 306-315 deg.) found Libya-Isidis Regio
quite bright at the evening terminator, but Hellas to the south was not
conspicuously light. On Feb 1 (CML = 71 deg.) Warell (45-cm refl.) saw a broad
a.m. limb haze with a local brightening over Olympus Mons. Devadas failed to
see Edom as a separate bright area but several times found the general N.
border of Sinus Sabaeus rather bright, perhaps affected by light hazes.
Edom-Thymiamata was light to McKim on the morning limb on Feb 8. Chryse
remained rather bright both at the evening terminator and on the morning limb.
Richard McKim, Director
1997 February 16th
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January 1-31, 1997
From mckim@oundle.northants.sch.uk Mon Feb 10 13:45:24 1997
Mars, 1996-97: British Astronomical Association:
Fourth Report on observations 1997 January 1-31
General
The disk diameter increased from 8".0 to 10".6. I refer to published OAA
data (CMO No. 183) for comparison. New contributors this month were
P.Devadas (India), Prof. C.M.Gaskell (USA) and C.Meredith (UK). Others are
known to have unreported observations! The NASA probes are en route, but Mars 96,
the Russian one, failed; the latest details have been given in Sky and
Telescope, 1997 March, page 20 and elsewhere. William Sheehan's excellent
new Mars book is also reviewed in the latter magazine.
North Polar Region
The North Cap remained large and bright to all observers, with a dark collar.
No colour other than white has been directly reported to the Director in the
period reviewed, but in CMO No.183 H.Ishadoh (31-cm refl.) is reported to
have noticed a slight dullness coupled with a brownish tint "from November or
before", until Dec 16. The Japanese account fails to mention any particular
CM longitude (or CML range), which may be important. From Dec 24 the cap
seemed normally bright again to Ishadoh; the brownish tint partly confirms
Schmude's December 20 observation (see BAA Report No. 3). Few UK observations
for December are to hand; they reveal nothing unusual (nor do the other
Japanese data). Devadas commented that by Jan 14 the NPC seemed perceptibly
smaller than earlier, which is to be expected from the seasonal date.
The Director has not yet measured any of the images submitted for latitude.
Surface features
In the second half of December and the first half of January, OAA observers
remarked upon the colour contrast between the bluish maria to the south and
the brownish Utopia to the north. Doubtless these apparent tints will differ
from their true colours, but the difference in hue is undoubtedly real. This
difference has been remarked upon very many times by past observers at
aphelic apparitions: for example, the BAA Mars Section in 1935, G.de Mottoni
in his beautiful coloured charts for 1952, Capen in the 1960s, Antoniadi and
Slipher in their observational notes, and in the seasonably comparable epoch
of the early 1980s by the BAA and other organisations. Devadas (36-cm refl.)
on Jan 20 saw Solis Lacus well: it was quite large and dark, as in 1995. (Is it
finally fading again on the southern following side, as noticed in the 1995 CCD
images?) Tithonius L. and Phoenicus L. were also well-marked. Devadas and
Meredith found the foreshortened Mare Sirenum somewhat poorly defined. Some of
the martian volcanoes have shown up on mid-disk as dusky spots this month.
Dust storms (yellow clouds)
The deserts appeared their characteristic light orange, dust-free colour.
White clouds
Examples only, given that many observations still remain unreported: Devadas,
Jan 4, CML 253 deg., Elysium lightish preceeding the CM; morning cloud over
N. Aeria-Arabia. Devadas, Jan 14, CML 157 deg., Elysium lightish on the morning limb.
[OAA observers found Elysium quite dull or only slightly light on the evening side
(late Dec to early Jan), but light to the west of Propontis I, when immersed in the a.m.
limb haze (mid-Jan). They found Alba apparently variable; in mid-Jan it was sometimes
lightish from midday to evening]. Devadas, Jan 20, CML 96 deg., Chryse-Xanthe bright on
evening terminator, and Arcadia-Tempe lightish on mid-disk. Warell emailed the Director
that the Tharsis orographic clouds were "very evident" on Jan 24.
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