  We report on mapping of the south polar region of Mars using data from the
Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument. Our
observations have led to the following discoveries: 1. Water ice is present in
the form of pole-circling clouds originating from the circum-Hellas region,
beginning prior to Ls=162 and diminishing markedly at Ls=200-204. 2. It has
previously been inferred by temperature measurements(Titus et al., 2003) and
CO2-H2O mixture spectral models (Langevin et al., 2007) that surface water ice
was present in the Cryptic Region in the final stages of sublimation. The high
resolution of CRISM has revealed regions where only water ice is present (not a
CO2-H2O ice mixture). This water ice disappears completely by Ls=252 and may be
the source of water vapor observed by CRISM in southern latitudes between
Ls=240-260 (Smith, et al., this issue). 3. We have estimated surface CO2 ice
grain size distributions for the South Pole Residual Cap (SPRC) and the
seasonal CO2 ice cap that covers it throughout summer spring and summer. Our
analysis suggests that grain sizes peak at Ls=191-199 with an apparent grain
size of ~7 +/-1 cm. By the end of the summer period our analysis demonstrates
minimum apparent grain sizes of ~5 +/-1 mm predominate in the SPRC. 4. Fine
grained CO2 ice condenses from Ls=0-40, and extends symmetrically away from the
geographic pole, extending beyond 80 deg S by Ls=4-10. No evidence for unusual
CO2 depositional processes in the Cryptic Region is observed up to Ls=16.

Earth and Planetary Astrophysics