Sedimentary Facies Observed by the Curiosity Rover at Gale Crater, Mars

Since landing in Gale crater, the Mars Science Laboratory (MSL) Curiosity rover has investigated more than 75 m of stratigraphy, revealing a rich array of clastic sedimentary rocks. Data from the Mastcam, Navcam, Mars Hand... [ view full abstract ]

Since landing in Gale crater, the Mars Science Laboratory (MSL) Curiosity rover has investigated more than 75 m of stratigraphy, revealing a rich array of clastic sedimentary rocks. Data from the Mastcam, Navcam, Mars Hand Lens Imager (MAHLI) and ChemCam instruments are used to identify distinct sedimentary facies. Facies are distinguished on the basis of grain properties, sedimentary structures, outcrop erosional resistance and color.

Over the past 3 years, Curiosity has traversed more than 11 km across Aeolis Palus to the rover’s current location on the lower north slope of Aeolis Mons (informally known as Mt. Sharp). During this traverse, Curiosity stopped at several geologic waypoints. Observations acquired along the traverse enabled the recognition of several key facies transitions.

Early in the mission, Curiosity investigated the Yellowknife Bay formation, which consists of a mudstone, massive-bedded sandstones, cross-stratified sandstones, and conglomerates deposited in a fluvial and lacustrine setting. As the rover drove further up-section to the southwest, Curiosity encountered inclined sandstone and conglomerate beds of the Kimberley formation, interpreted to represent delta clinoforms. Even further up-section, finely laminated mudstones were observed in the Murray formation. Minor amounts of fine-grained, evenly laminated sandstones with bimodal dip directions were also identified, which are interpreted as deposits of reversing flows in an eolian environment. Placed in spatial and stratigraphic context, these facies provide evidence for persistent fluvial activity, transitioning down gradient into delta clinoforms and lacustrine mudstones. Minor amounts of eolian pinstripe laminae deposited on top of fluvial sandstones and clinoforms suggest that there were intermittent dry periods. Near the Dingo Gap field site, channels incised into underlying sandstones suggest a drop in base level. Elsewhere, lacustrine mudstones occur at higher elevation than fluvial and eolian deposits, suggesting a rise in lake level. Collectively, these facies record the progressive infilling of Gale crater, and show that it contained a rich aqueous history with evidence for fluctuating lake levels.