Smectite deposits in Marathon Valley, Endeavour Crater, Mars, identified using CRISM hyperspectral reflectance data

Abstract

The ~100 m wide Marathon Valley crosscuts the Cape Tribulation rim segment of the 22 km diameter, Noachian‐age Endeavour impact crater on Mars. Single‐scattering albedo spectra retrieved from three Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) Full‐Resolution Targeted (FRT, regularized to 18 m/pixel) and two Along Track Oversampled (ATO, regularized to 12 m/pixel) observations indicate the presence of Fe3+‐Mg2+ smectite exposures located in Marathon Valley with combination vibration metal‐OH absorption strength comparable to smectite spectral signatures in Mawrth Vallis. The Opportunity rover was directed to the exposures and documented the presence of Shoemaker formation impact breccias that have been isochemically altered, likely by fracture‐controlled aqueous fluids.

The structural, stratigraphic, and paleoenvironmental record exposed on the rim and walls of Iazu Crater, Mars

“…Individual spectra retrieved show how the existence of Fe 3+ ─Mg 2+ smectites is inferred from the presence of 1.9, 2.3, and 2.4 μm absorptions (Figure ). The average depth of the 2.3 μm absorption in the pixels shown is 0.0145 ± 0.005, comparable to that in detections in Marathon Valley [ Fox et al , ]. This feature is broader than absorptions seen in laboratory measurements for nontronite or saponite and positioned at an intermediate wavelength.…”

“…From a global viewpoint the Martian rock record preserves evidence of diverse ancient environments with much greater water availability in the past. Phyllosilicate minerals have been identified, largely dating to the Noachian period (4.1–3.7 Gyr), that formed by alteration in relatively neutral pH aqueous environments [ Poulet et al , ; Bibring et al , ; Bishop et al , ; Ehlmann et al , ; Ehlmann and Edwards , ; Arvidson et al , ; Fox et al , ]. Global environmental change beginning late in the Noachian and through the Hesperian (3.7–3.1 Gyr) led to decreased water availability, a change in fluvial channel morphology consistent with decreased erosion rates [ Andrews‐Hanna and Lewis , ], and the formation of hydrated sulfate‐bearing deposits preferentially in low‐lying areas [ Bibring et al , ].…”

Diverse Lithologies and Alteration Events on the Rim of Noachian‐Aged Endeavour Crater, Meridiani Planum, Mars: In Situ Compositional Evidence

“…Erosion has variably degraded the crater rims with on the order of 100–200 m having been removed, mostly before deposition of the Burns formation sands (Crumpler, Arvidson, Bell, et al, ; Grant et al, ). Some of the rim segments show the infrared spectral signature of Fe‐Mg‐smectite clays in data returned by the CRISM instrument on board Mars Reconnaissance Orbiter (Fox et al, ; Noe Dobrea et al, ; Wray et al, ), suggesting that they have undergone aqueous alteration under conditions of circumneutral pH. A localized area in the region explored by Opportunity during the sols covered here has yielded detections of phyllosilicates by CRISM (Figure c).…”

Widespread exposure of Noachian phyllosilicates in the Margaritifer region of Mars: Implications for paleohydrology and astrobiological detection

“…Mineralogical detections in the study region (black outline) in their wider context. Deep colors: this study, pastels: detections by other workers [ Wiseman et al ., ; Wray et al ., ; Flahaut et al ., ; Lichtenberg et al ., ; Milliken and Bish , ; Osterloo et al ., ; Grant et al ., ; Sowe et al ., , ; Le Deit et al ., ; Wilson et al ., ; Fox et al ., ; Salvatore et al ., ]. Base: hillshade from MOLA data [ Smith et al ., ].…”