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Bagnold Dunes Campaign Phase 2: Visible/Near‐Infrared Reflectance Spectroscopy of Longitudinal Ripple Sands

2018; American Geophysical Union; Volume: 45; Issue: 18 Linguagem: Inglês

10.1029/2018gl079025

1944-8007

J. R. Johnson, J. F. Bell, Steve Bender, E. A. Cloutis, B. L. Ehlmann, A. A. Fraeman, O. Gasnault, S. Maurice, P. Pinet, L. M. Thompson, Danika Wellington, R. C. Wiens,

Aeolian processes and effects

Abstract As part of the Phase 2 Bagnold Dune campaign at Gale Crater, Mars, constraints on the geochemistry, mineralogy, and oxidation state of pristine and disturbed linear sand ripples were made using visible/near‐infrared spectral observations for comparison to Phase 1 spectra of the barchan dunes to the north. Spectra acquired by the ChemCam and Mastcam instruments (400–1,000 nm) at four Phase 2 locations revealed similar overall spectral trends between the two regions, but most Phase 2 sands were redder in the visible wavelengths. The majority of targets exhibited lower red/infrared ratios, higher ~530‐nm band depths, and higher red/blue ratios than Phase 1 samples, suggesting a greater proportion of redder, fine‐grained, ferric sands in Phase 2 samples. This is consistent with the slightly greater proportion of hematite in Phase 2 samples as determined from CheMin analyses of the Ogunquit sands, which may reflect contamination from the surrounding hematite‐bearing Murray formation bedrock.