2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 21-2
Presentation Time: 8:20 AM


FRAEMAN, Abigail A., California Institute of Technology, Pasadena, CA 91106, EDWARDS, Christopher S., Flagstaff, AZ 86001, EHLMANN, Bethany L., Division of Geological and Planetary Sciences, California Institute of Technology, MC170-25, Pasadena, CA 91125, ARVIDSON, Raymond E., Earth & Planetary Sciences, Washington University in St. Louis, 1 Brookings Drive, Saint Louis, MO 63130, HORGAN, Briony H., EAPS Department, Purdue University, West Lafayette, IN 47907 and RICE, Melissa S., Geology Department, Western Washington University, 516 High St, Bellingham, WA 98225, afraeman@caltech.edu

We map lower Mt. Sharp (formally known as Aeolis Mons) using CRISM, HiRISE, and THEMIS derived thermal inertia (TI) to provide geologic context for Curiosity’s in situ investigation of the area and to develop testable hypotheses about its geologic history. Results also feed into traverse planning in helping to locate scientifically valuable and accessible targets for in situ analyses. We generate improved mineral maps from 18 m/pixel CRISM data using supervised classification methods, and processed along-track oversampled (ATO) CRISM data to 12 m/pixel using an iterative log maximum likelihood method with penalty function regularization. Updated TI values of the area were generated using pixel specific albedo, elevation, and slope. HiRISE data over Mt. Sharp’s oldest unit, the Murray formation, show color variations at the sub-meter scale. New CRISM products highlight isolated outcrops that contain iron oxides, sulfates, hydrated material, and a spectral feature at 2.2 µm due to Al-OH or Si-OH bearing material. These variations are not laterally continuous, suggesting the processes that formed alteration phases within this unit were localized. CRISM ATO data over Pahrump Hills within the Murray formation have unique VNIR spectral properties, possibly related to presence of ~8 wt% hematite within this area. TI values within the Murray formation cluster into two distinct groups having mean values of ~275 and ~225 TI units. Differences in TI are due to variations in sand cover and degree of induration, which could be linked to the nature of cementation or post-depositional diagenesis. Curiosity’s planned traverse crosses through both TI groups. Two localized deposits of crystalline hematite are present within and above the Murray formation, and the disparate strategic positions suggest that they either formed through secondary alteration processes that occurred in multiple locations or processes that deposited them were not unique to a single point in time. Located stratigraphically above the hematite unit, we also map an Fe(II)-bearing unit. We also identify an unconformable draping material with high TI (indicating a higher degree of cementation and/or larger particle sizes), which can be mapped as two separate units with distinct morphologies and spectral properties.