Abstract
Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where orbital spectral reflectance signatures indicate the presence of Fe(+3)-rich smectites. The signatures are associated with fine-grained, layered rocks containing spherules of diagenetic or impact origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is thus preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.
Highlights
Crater, where orbital spectral reflectance signatures indicate the presence of Fe+3-rich smectites
The layered rocks are overlain by breccias and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact
Evidence is preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfaterich rocks at Meridiani Planum
Summary
Crater, where orbital spectral reflectance signatures indicate the presence of Fe+3-rich smectites. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Observations from the Mars Reconnaissance Orbiter’s Compact Imaging Spectrometer for Mars (CRISM) [3, 4], acquired in an along track oversampled (ATO) mode to sharpen spatial details, were used to identify and map a Fe+3-rich smectite mineral locality in an area on the eastern side of Cape York called Matijevic Hill [5] (Fig. 1).
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