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This page contains a collection of images of Mars obtained from the
NASA IRTF during the 1994-95 and 1996-97 apparitions. The images were
obtained by Jim Bell, Bill Golisch, Dave Griep, Charlie Kaminski,
Christophe Dumas, and Jeff Moersch.
February 17, 1997 IRTF image, compared to HST
Left: This 2.331 micron near-IR image of Mars was obtained from the NASA IRTF
telescope at 12:27 UT on February 17, 1997. Observers: Bell, Golisch, Moersch.
This may very well be the best groundbased near-IR image of Mars ever obtained!
the resolution to be approximately 40-50 km/pixel. For a few sweet but brief
hours that night, it was as if the skies parted and there was no atmosphere
above us at all!!! Judging from the excellent image resolution, it would
appear that there is very little, if any, dust activity in this region of
Mars at this time.
Right: HST image of the same hemisphere of Mars obtained at a wavelength
of 1.042 microns on February 26, 1995.
February 17, 1997 IRTF Mars seeing movie
This is a "virtual telescope" MPEG movie that demonstrates the
in seeing that affect telescopic image quality. Shown is a sequence of
500 images obtained at 30 millisecond intervals on the night of February
17, 1997. The images were obtained from the NASA Infrared Telescope
Facility (IRTF) at Mauna Kea Observatory, Hawaii, at an infrared
wavelength of 2.331 microns. The observers were Jim Bell and Jeff Moersch
from Cornell University and Bill Golisch from the IRTF.
Playing the image back at a frame rate of 30 msec/frame yields a "real time"
movie showing what Mars would look like if you were peering through the
eyepiece of the 3-meter telescope on Mauna Kea (that is, of course, if
the telescope actually HAD an eyepiece...). The wiggling of the planet
from frame to frame is caused by the slight movement of the telescope
by the wind; beneath this wiggling you can see variations in the seeing
or fuzziness of the atmosphere. For a few of the frames in this movie,
the seeing is exceptional! Can you find these magic frames?
February 15-16, 1997 Lowell and IRTF images
Left: RGB Composite image of Mars obtained from the Lowell Observatory 31" telescope at 8:06 UT
on February 15, 1997. Observers: Bell, Moersch, Martin, Howell.
Right: 3.58 micron image of Mars obtained from the NASA IRTF telescope at 10:28 UT
on February 16, 1997. Observers: Bell, Golisch, Moersch.
8 December 1996 IRTF images
1995 AAS/DPS Presentation in Kona
Time-series mosaic (77649 bytes)
Feb. 4 1995 Mosaic (347613 bytes)
Dec. 27 1994 Mosaic (146938 bytes)
January 14, 1995 (A, B, C) and
February 1, 1995 (D, E, F)
with PCA results
IRTF images and Principal Components Analysis (PCA) results from 14 JAN 95
(A, B, and C) and 1 FEB 95 (D, E, F). Images A and D are contimuum wavelength
(2.25µm) images shown for comparison to the PCA results. In image A the
prominant dark feature west of the sub-Earth point is Syrtis Major. In
image D the prominant central dark feature is Acidalia.
PCA transforms the data set from a space of wavelengths to a space of
eigenvectors which lie along progessively decreasing variation. The greatest
variaition is surface albedo and so this is the first principal component.
The next greatest variation to come out of PCA is a trait related to temperature
and water ice content. Images B and E show how each region relates to this trait.
Bright areas such as the polar regions and morning and evening regions are high
in this trait and centrally located, warmer, dark regions have a negative
correlation with this trait.
Areas with extreme correlations of the first two principal components are then
taken to be spectral endmember regions and the disk is modeled as a linear combination
of these endmember regions. The north polar region is taken as an endmember due
to its high correlation with the temperature/ice principal component. Images C and
F are maps of the fractional abundance of the north polar region spectral endmember
and morning and evening regions show up to 50% composition. This indicates that
these regions are cold and to some degree covered with water frosts. Note that
in these images the entire disk is not modeled. Regions too near the limb
are dominated by non-linear processes in their spectra and so are left unmodeled
by this linear technique.
Sinton bands in February 1995 IRTF images
Spectral absorption features were seen at 3.33 and 3.4µm in the
classic dark albedo region Syrtis Major (seen in the images bounded by
latitudes 0-30° and longitudes 270-300°) of IRTF images from February
1 (A and B) and February 4 (C and D) 1995. The features lie close to absorption
features reported by Sinton (1959 Science, 130, 1234-1237) which he attributed
to the effect of organic material on the surface of Mars. There are no
matching features in modeled Mars atmospheric spectra nor in water ice and
HDO (an explanation of the two longest wavelength Sinton Bands). There are
similar features in carbonates (e.g. calcite) but the Syrtis spectrum
shows no carbonate features at 4µm. There is a similarity of these
features with C-H absorptions in methane which opens the posibility of organics
on Mars. However, carbonate or sulfate mineralogy has not yet been ruled out
and much work still needs to be done.
The images next to the spectral plots are relative band depth maps (RBDM).
These maps are the ratio of the image at the absorption wavelength (3.331µm for
A and C, and 3.401µm for B and D) to a continuum image at that wavelength
calculated from linear interpolation of two nearby local continuum images
(at 3.194 and 3.497µm). In all images but B, Syrtis Major appears as a
5-10% absorption feature. In the 3.4µ RBDM water ice can dominate the map
and thus the disappearance of Syrtis Major relative to the surrounding area
due to the effects of evening water ice clouds.
For information contact Jim Bell
Mail to: firstname.lastname@example.org