The goals of our proposed work are to perform quantitative unmixing of carbonate-bearing lithologies across mars and determine (1) carbonate, phyllosilicate, and other mineral abundances, and…

This is a $371,915.30 research grant awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to The Research Foundation For The State University Of New York, doing business as Stony Brook University. The goal of the proposed work is to perform quantitative unmixing of carbonate-bearing lithologies across Mars and determine the carbonate, phyllosilicate, and other mineral abundances, as well as constrain the inventory of carbon dioxide in carbonate-bearing rocks in the Martian crust. The grant funds several tasks including atmospheric corrections on Mars orbital spectroscopy data, mineral end-member identification, spectral mixture analysis, and integration with other Mars dataset analyses. This work is relevant to NASA's Mars Data Analysis Program as it aims to enhance the scientific data return from past and ongoing Mars orbital missions. The grant does not have a set-aside designation.

The goals of our proposed work are to perform quantitative unmixing of carbonate-bearing lithologies across mars and determine (1) carbonate, phyllosilicate, and other mineral abundances, and (2)constrain the inventory of CO􀁅2 in carbonate-bearing rocks in the martian crust. Carbonates can be indicative of neutral to alkaline depositional settings, potentially indicating habitable environments. They are also potential sinks for ancient martian CO2, although the degree to which they are responsible for loss of the ancient martian atmosphere is not tightly constrained. Carbonate outcrops have been identified and characterized in several noachian localities on the martian surface using visible/near- IR data from the compact reconnaissance imaging spectrometer for mars (crism) instrument (e.g., ehlmann ET AL., 2008; edwards and ehlmann, 2015; wray ET AL., 2016). Carbonates tend to be MG-bearing, although mixed-cation FE- and CA-bearing carbonates are also common, and tend to be older (wray ET AL., 2016). These detections are separate from the identification of ~2-5% carbonate in the globally homogenous fines by the mars global surveyor thermal emission spectrometer (MGS-TES; bandfield ET AL., 2003). Edwards and ehlmann (2015) used crism, TES, and themis data to constrain the carbonate abundance in nilli fossae to 5-15%. In-situ observations by the spirit rover identified carbonates at the 16-34 WT.% level in the comanche outcrop at gusev crater. Our own initial analyses of carbonate- and serpentine-bearing lithologies in mclaughlin crater show carbonate abundances of only 3-5%. The highly variable carbonate abundances determined from in situ and remote sensing measurements, as well as the different lithologies in which they occur could be caused by different formation mechanisms, ranging from surface/atmosphere interaction, to surface chemical sedimentation, to deep subsurface CO2 metasomatism among other processes. Our proposed work will help to constrain the formation mechanisms of carbonates on mars by determining abundances at each locality and correlating carbonate, phyllosilicate, and primary silicate abundances with geologic setting. To accomplish these goals, we will perform several tasks: (1) perform radiative transfer-based atmospheric corrections on crism l spectrometer data covering carbonate-bearing regions identified by ehlmann ET AL. (2008), bishop ET AL. (2013), edwards and ehlmann (2015), and wray ET AL. (2016) among other workers, (2), perform factor analysis and target transformation of crism images to isolate scene mineral end-members and constrain potential end-members for spectral unmixing, (3) in a small laboratory study, calculate robust vnir optical constants of relevant carbonates for use in spectral mixture analysis, (4) perform spectral mixture analysis on atmospherically corrected crism single scattering albedo images to constrain mineral abundances and particle sizes of carbonate-bearing deposits, (5) analyze atmospherically corrected TES and themis data for the largest carbonate-bearing deposits to provide additional constraints on carbonate abundance and thermophysical properties, and (6) coordinate compositional results with analyses of themis, CTX, hirise, and other imagery to tie carbonate abundances to specific geologic settings. This work is relevant to the mdap program because IT would enhance the scientific data return from the mars global surveyor, mars odyssey, and mars reconnaissance orbiter missions. The project is also relevant to mdap because IT includes􀁅analysis and comparison of mars orbital and surface data to increase the predictive accuracy of surface characteristics of mars from orbit.􀁅 our proposed tasks would identify carbonate and other spectral end-members within carbonate-bearing regions on mars, quantify the abundances of these phases, and constrain the geologic setting(s) and formation mechanism(s) of martian carbonate-bearing deposits.