Origin and composition of three heterolithic boulder- and cobble-bearing deposits overlying the Murray and Stimson formations, Gale Crater, Mars

Abstract

Here we present ground-based observations regarding a puzzling type of geological unit first observed prior to landing. Using ~25 cm/pixel High Resolution Imaging Science Experiment (HiRISE; McEwen et al., 2007) images acquired from the orbiting Mars Reconnaissance Orbiter (MRO), the team identified a suite of isolated features ranging in size from 10s to 100s of meters across that occur along the lower northern slopes of Aeolis Mons (informally, Mt. Sharp), the 5-km-high stratified mountain in Gale (Fig. 1). The strata of Aeolis Mons are sedimentary (Malin and Edgett, 2000; Anderson and Bell, 2010; Milliken et al., 2010). The puzzle was whether these isolated features are part of the sedimentary rock record (i.e., lithified units) or are younger, unconsolidated deposits.