HR: 09:30h
AN: P31D-07    [Abstracts]
TI: CRISM Observations of Water Vapor and Other Atmospheric Gases
AU: * Smith, M D
EM: Michael.D.Smith@nasa.gov
AF: NASA Goddard Space Flight Center, Code 693, Greenbelt, MD 20771, United States
AU: Wolff, M J
EM: wolff@spacescience.org
AF: Space Science Institute, 4750 Walnut St., Suite 205, Boulder, CO 80301, United States
AU: Clancy, R T
EM: clancy@spacescience.org
AF: Space Science Institute, 4750 Walnut St., Suite 205, Boulder, CO 80301, United States
AU: CRISM Team, T
EM: Michael.D.Smith@nasa.gov
AB: Near-infrared spectra returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on-board the Mars Reconnaissance Orbier (MRO) contain the clear spectral signature of several atmospheric gases including carbon dioxide (CO₂), water vapor (H₂O), and carbon monoxide (CO). Here we describe preliminary work on the seasonal and spatial mapping of atmospheric gases using CRISM, and the vertical profiling of water vapor and carbon monoxide made possible by one CRISM observation of the limb. The column abundance of atmospheric gases is retrieved by radiative transfer modeling of the CRISM spectra. We compute synthetic spectra using the correlated-k approximation for gas absorption and a discrete-ordinates approach to model aerosol scattering and the solar beam. Both CRISM hyperspectral (emission phase function) and multispectral observations can be used to map the column abundance of atmospheric gases as a function of season (L_s), latitude, and longitude. Results for water vapor show that the peak in water vapor abundance over the northern summer pole and its subsequent decrease and movement to the south are similar to what was observed by TES in previous martian years. The spatial variation of water vapor follows the expected positive correlations with surface pressure and albedo, and negative correlation with thermal inertia. The main observed variation of carbon monoxide is a direct correlation with surface pressure (or CO₂ abundance), with a mixing ratio of about 700 ppm. A single observation by CRISM of the limb (L_s=149°, near the north pole) shows a close correspondence between the vertical dependence of CO and CO₂ indicating that at this location CO is well-mixed with the background CO₂ gas. On the other hand, the vertical distribution of water vapor appears to be noticeably more confined toward the surface than CO₂ given the more rapid decrease with height of the water vapor signal.
DE: 0343 Planetary atmospheres (5210, 5405, 5704)
DE: 5405 Atmospheres (0343, 1060)
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting