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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! We estimate 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 moment-to-moment variations 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 (GIF, 40K) (TIFF, 61K)

    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)
    IRTF images 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
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