Mineralogy and fluvial history of the watersheds of Gale, Knobel, and Sharp craters: A regional context for the Mars Science Laboratory Curiosity's exploration

Abstract

A 500 km long network of valleys extends from Herschel crater to Gale, Knobel, and Sharp craters.The mineralogy and timing of fluvial activity in these watersheds provide a regional framework for deciphering the origin of sediments of Gale crater's Mount Sharp, an exploration target for the Curiosity rover. Olivine-bearing bedrock is exposed throughout the region, and its erosion contributed to widespread olivine-bearing sand dunes. Fe/Mg phyllosilicates are found in both bedrock and sediments, implying that materials deposited in Gale crater may have inherited clay minerals, transported from the watershed. While some topographic lows of the Sharp-Knobel watershed host chloride salts, the only salts detected in the Gale watershed are sulfates within Mount Sharp, implying regional or temporal differences in water chemistry. Crater counts indicate progressively more spatially localized aqueous activity: large-scale valley network activity ceased by the early Hesperian, though later Hesperian/Amazonian fluvial activity continued near Gale and Sharp craters.

Mineralogy and stratigraphy of the Gale crater rim, wall, and floor units

“…These spectra are also distinct from the stratigraphic layer containing nontronite in Mount Sharp identified by Milliken et al . [], as previously reported for a few select locales [ Ehlmann and Buz , ]. The Mount Sharp spectra are most similar to Al‐substituted nontronite due to the absorption shoulder at ~2.24 μm, an Al,Fe‐OH vibration [ Milliken et al ., ].…”

Modeling the thermal and physical evolution of Mount Sharp's sedimentary rocks, Gale Crater, Mars: Implications for diagenesis on the MSL Curiosity rover traverse

“…However, the stratigraphic relationships between Yellowknife Bay sediments and other units are not entirely certain, and the deposit might instead represent a late‐stage unit from Peace Vallis alluvial activity emplaced atop materials left behind during Mount Sharp's retreat [ Grotzinger et al , ]. There are smectite clays in the Gale Crater watershed which could have been delivered to the vicinity [ Ehlmann and Buz , ]. Continued analysis of orbital and in situ data to understand contact relationships and the timing of sedimentation and clay formation is crucial.…”

“…Smectite clays, a type of phyllosilicate formed during the reaction of water with silicates, have been detected from orbit in Mount Sharp units [ Milliken et al , ], regionally within the watershed of Gale Crater [ Ehlmann and Buz , ], as well as found in situ by the Curiosity rover Chemistry & Mineralogy (CheMin) X‐Ray Diffraction (XRD) instrument at multiple traverse locations [ Vaniman et al , ]. Smectites should be a key tracer of diagnetic history because at elevated temperatures they are no longer a thermodynamically stable phase and instead convert to other phyllosilicate phases like illite or chlorite that lack interlayer water via a series of intermediate reactions to form mixed layer clays like illite‐smectite or chlorite‐smectite [e.g.…”

Reconstructing the past climate at Gale crater, Mars, from hydrological modeling of late‐stage lakes

“…Many of these southern highland craters exhibit evidence for open-and closed-basin lakes (Figure 1a) [Cabrol and Grin, 1999;Fassett and Head, 2008] including Sharp crater to the west of Gale, found to have fan deposits and a similar mineralogy as Gale crater [Ehlmann and Buz, 2015]. Many of these southern highland craters exhibit evidence for open-and closed-basin lakes (Figure 1a) [Cabrol and Grin, 1999;Fassett and Head, 2008] including Sharp crater to the west of Gale, found to have fan deposits and a similar mineralogy as Gale crater [Ehlmann and Buz, 2015].…”