Mineral Diversity and Crystal Chemistry at Gale Crater, Mars from the CheMin X-ray Diffractometer
The Mars Science Laboratory Curiosity rover arrived in Gale Crater in August 2012 with a primary goal of characterizing the habitability of ancient and modern environments. Curiosity landed in Gale Crater to study a sequence of ~3.5 Ga old sedimentary rocks that, based on orbital spectroscopy, contain secondary minerals that suggest deposition and/or alteration in liquid water. The sedimentary sequence that composes the lower slopes of Mount Sharp within Gale Crater may preserve a dramatic shift on early Mars from a relatively warm and wet climate to a cold and dry climate based on a transition from smectite-bearing to sulfate-bearing strata. The Chemistry and Mineralogy (CheMin) instrument is one of two internal laboratories on Curiosity and includes a transmission X-ray diffractometer (XRD) and X-ray fluorescence (XRF) spectrometer. CheMin measures loose sediment samples scooped from the surface and drilled rock powders and provides quantitative mineralogy to a detection limit of ~1 wt.%. Curiosity has primarily been exploring the site of a predominantly ancient lake environment. Here, we discuss the results from CheMin, which demonstrate an astounding diversity in the mineralogy of fluvio-lacustrine rocks that signify variations in source rock composition, sediment transport mechanisms, and depositional and diagenetic fluid chemistry.
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