Mars odyssey gamma RAY spectrometer (GRS) mapping indicates that the chemical variability of the martian subsurface is subdued at the approximately 450 KM spatial scales relative to both earth and…

Mars odyssey gamma RAY spectrometer (GRS) mapping indicates that the chemical variability of the martian subsurface is subdued at the approximately 450 KM spatial scales relative to both earth and moon. Nevertheless, our recent investigations with odyssey GRS data have revealed statistically significant 'chemically striking regions'. As described in section 2 of the proposal, these are midlatitudinal areas where the subsurface compositions of two or more elements deviate significantly from the corresponding global averages. Our studies also developed a robust approach to integrate infrared spectral information from orbit, radar observations from earth, imaging from orbit, and in situ chemical data at the two mars exploration rover (MER) sites, not only to constrain genetic processes but also to reveal the most likely scenarios of origin in a pilot study of one such region. Termed rave by US, this region in the vicinity of daedalia planum is marked by the simultaneous depletion of FE and SI. The synthesis of multiple datasets enabled US to infer that rave is likely to contain fines, with chemical composition and physical properties similar to surface dust at the two MER sites, diluted and indurated by a minor component. We find that sulfates containing some combination of CA and MG to be the most likely minor component. Our inferences converge well with martian climate models suggesting significant H20(S) precipitation in the area several million years ago succeeded by an arid climate.this proposal outlines a research program that will further develop and apply our pilot-study methodology at two other regions that are chemically striking and of broad geological interest: (1) elysium lava flows and (2) the greater thaumasia plateau. Elysium is one of the few areas on mars where mapped geologic units and chemical data are internally coherent. Even though IR-derived mineralogical analysis over elysium is prevented by fine-grained deposits that obscure the underlying lava flows, we propose that the GRS chemical data, mapped geologic units, thermally-derived physical properties, and hirise images will reveal and constrain the underlying geologic processes of this region. In contrast, the greater thaumasia plateau has the benefit of being less obscured by fine-grained surficial deposits, enabling complementary insight from visible/near/thermal-infrared data. In addition, we will test recent controversial models that propose the existence of complex tectonic features in this region using the suite of chemical, mineralogic, and morphologic information that will be evaluated in this study. This research program is relevant to the mars exploration program. The findings of the two tasks will provide direct insight into the geological character of the martian subsurface at the hundreds-of-kilometer lateral scale and provide insight into the manner by which processes in the martian near subsurface (tens of centimeter depths) are coupled to deeper crustal processes. Accordingly, this research effort will directly address ~epag objectives III.a and III.B by (1) contributing to our understanding of the nature and evolution of martian geological processes and (2) characterizing the nature of the martian interior. This proposal is being submitted for consideration for an early career fellowship for the PI who is currently a postdoctoral research associate under the supervision of the institutional P.I.