Thermal Inertia and Albedo Mapping of Juventae Chasma

Details Thermal Inertia and Albedo Mapping of Juventae Chasma Thermal Inertia and Albedo Mapping of Juventae Chasma

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004dps....36.3808w&link_type=abstract

American Astronomical Society, DPS meeting #36, #38.08; Bulletin of the American Astronomical Society, Vol. 36, p.1161

Astronomy and Astrophysics

Astronomy

Scientific paper

The origin and composition of the layered light-toned formations (LLF) found in Valles Marineris and neighboring chasms in the Martian tropics have remained a mystery for over 30 years since their discovery [Sharp 1973]. One intriguing possibility is that they are sedimentary deposits formed in ancient ice-covered lakes [Lucchitta et al. 1992], but volcanic origins have also been proposed [Chapman et al. 2003].
Spectroscopic methods of determining surface composition can often be frustrated by the ubiquitous Martian dust cover or by surface texture and particle size effects that reduce spectral contrast [Kirkland et al. 2003]. Measuring the thermal properties of Martian surface materials can also provide clues about composition and physical characteristics, and has the advantage of probing the surface to a greater depth.
We present new high-resolution maps (100 m/pixel) of thermal inertia (TI) and albedo (A) for several LLF's in Juventae Chasma and Ganges Chasma, and comparison features such as White Rock in Pollack Crater. These maps were derived from infrared observations by the Mars Odyssey Thermal Emission Imaging System (THEMIS) using a 1-D finite-difference, time-stepping thermal model which accounts for the effects of surface slope and orientation on insolation rates. MOLA topography data (128 pixel/deg) was used to estimate surface slopes.
Most previous calculations of TI based on the lower-resolution data from Mars Global Surveyor (> 3 km/pixel) used only nighttime temperature observations. While this approach is valid over the typical range of TI values on Mars, for TI > 400 J m-2 K-1 s-1/2 the surface has sufficient ``memory" of the daytime temperature that uncertainties in the albedo value become important. Therefore we only map areas which have both a daytime (3pm - 5pm) and a nighttime (3am -5am) THEMIS image, and solve for the best-fit values of I and A simultaneously.

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