Hematite-Bearing Materials on Mars Identified and Characterized Using MRO CRISM, Opportunity, and Curiosity Data

Abstract:

Crystalline hematite has been detected in several locations on Mars using orbital spectral data, most recently through analysis of Mars Reconnaissance Orbiter CRISM hyperspectral imaging data. However, there are only two locations where crystalline hematite have been identified and characterized using both orbital and rover-based observations. These include the Vera Rubin ridge on the northern slopes of Mount Sharp in Gale Crater, and Meridiani Planum. The Vera Rubin ridge was identified on the basis of strong electronic bands associated with red hematite in CRISM spectra, and was characterized in detail using Curiosity’s array of instrumentation. Rover-based observations clearly demonstrate that groundwater-induced diagenesis affected the spectral properties of the hematite occurrences in the Murray formation sedimentary strata on the ridge and below. On the other hand, Opportunity rover observations have shown that the orbital-based detections of hematite in Meridiani Planum are due to surface concentrations of gray hematitic concretions weathered from the sulfate-bearing Burns formation rocks and left behind as wind-blown lag deposits. The concretions are interpreted to be diagenetic in origin due to groundwater flowing through the Burns formation strata. We have used nonlinear modeling of CRISM spectra and Opportunity imaging data to demonstrate that spectral detections of hematite correspond to relatively high surface abundances of concretions. These locations correspond to wind-swept regions in and around craters, with increased concentrations interpreted to be lag deposits in association with coarse-grained basaltic sands. Two locations and two rather different reasons for the orbital detections of crystalline hematite reinforce the geologic complexity of Mars, although both occurrences involve post-depositional diagenesis.