PIA02333: Dark Dry Ice on Southern Cap - Thermal Image
Target Name: Mars
Is a satellite of: Sol (our sun)
Mission: Mars Global Surveyor (MGS)
Spacecraft: Mars Global Surveyor Orbiter
Instrument: Thermal Emission Spectrometer
Product Size: 500 x 500 pixels (width x height)
Produced By: U.S. Geological Survey
Producer ID: MRPS95225
P50565
Addition Date: 1999-09-18
Primary Data Set: MGS EDRs
Full-Res TIFF: PIA02333.tif (199.5 kB)
Full-Res JPEG: PIA02333.jpg (44.24 kB)

Click on the image above to download a moderately sized image in JPEG format (possibly reduced in size from original)

Original Caption Released with Image:

The early part of the Mars Global Surveyor mission provided good TES coverage of the Mars south polar region. These data allow mapping of the polar cap recession, surface and atmospheric temperatures, and albedo features found within the seasonal cap itself (Kieffer et al., 1998, Titus et al., 1998).

During the period observed, the seasonal south polar cap retreated continuously and asymmetrically around the geographic pole, much the way Viking observed in 1976-1977 (Kieffer et al., 1977). One of the most dominant albedo features on the seasonal cap is a region that appears almost as dark as bare ground, but yet remains cold. We refer to this region, generally located between latitudes 85S and 75S and longitudes 150W and 310W, as the Cryptic region.

A re-examination of the IRTM data revealed that the Cryptic region was not unique to the TES era, but also was quite apparent during the Viking era. Interesting enough, Antoniadi (Blunck, 1977) observed dark regions forming on the season cap that loosely correlates to the Cryptic region: Depressio Magna (1909) and Depressio Parva (1929). These depressios were located at 270 W, 78S and 166 W, 76S, respectively.

Analysis of both the TES and IRTM data indicate that the Cryptic region is unique in its thermophysical properties relative to the rest of the cap. The region is a repeatable event that occupies the same general area from year to year. It is darker and slightly warmer than the rest of the south polar cap. Even though the Cryptic region is slightly warmer, it must still be CO2 buffered since it remains "cold" for several days.

Spectral analysis of the TES longward of the 15 micron atmospheric band shows that the Cryptic region shows less spectral than the rest of the polar cap. This suggests that the region may be composed of "ice," as opposed to snow or frost (Hansen, 1998). Further spectral analysis on going.

This image is a map of TES data, showing TES "T20" of the south polar cap. (The TES "T20" is a synthetic band created by convolving the response function of the IRTM 20m filter with the TES spectra.)The image is a composite from the first rolls of orbit 43 (Ls =219.2, Nov 17, 1997) and orbit 45 (Ls=220.8, Nov 20, 1997). The Cryptic region is the blue area curving along the 80S latitude line. The region shows up in this image as only slightly warmer than the rest of the polar cap, but still too cold to be bare ground.

See also the Lambert Albedo Image PIA02332.

Image Credit:
NASA/JPL/USGS Flagstaff

Image Addition Date:
1999-09-18