MAHLI at the Rocknest sand shadow: Science and science‐enabling activities

Abstract

During Martian solar days 57–100, the Mars Science Laboratory Curiosity rover acquired and processed a solid (sediment) sample and analyzed its mineralogy and geochemistry with the Chemistry and Mineralogy and Sample Analysis at Mars instruments. An aeolian deposit—herein referred to as the Rocknest sand shadow—was inferred to represent a global average soil composition and selected for study to facilitate integration of analytical results with observations from earlier missions. During first‐time activities, the Mars Hand Lens Imager (MAHLI) was used to support both science and engineering activities related to sample assessment, collection, and delivery. Here we report on MAHLI activities that directly supported sample analysis and provide MAHLI observations regarding the grain‐scale characteristics of the Rocknest sand shadow. MAHLI imaging confirms that the Rocknest sand shadow is one of a family of bimodal aeolian accumulations on Mars—similar to the coarse‐grained ripples interrogated by the Mars Exploration Rovers Spirit and Opportunity—in which a surface veneer of coarse‐grained sediment stabilizes predominantly fine‐grained sediment of the deposit interior. The similarity in grain size distribution of these geographically disparate deposits support the widespread occurrence of bimodal aeolian transport on Mars. We suggest that preservation of bimodal aeolian deposits may be characteristic of regions of active deflation, where winnowing of the fine‐sediment fraction results in a relatively low sediment load and a preferential increase in the coarse‐grained fraction of the sediment load. The compositional similarity of Martian aeolian deposits supports the potential for global redistribution of fine‐grained components, combined with potential local contributions.

Gale crater and impact processes – Curiosity’s first 364 Sols on Mars

“…Within Gale crater stratigraphy, no discrete horizons of spherules have yet been identified. Rather, candidate impact spherules occur prominently within disturbed soils, such as those found during investigation of the Rocknest wind drift (Blake et al, 2013;Minitti et al, 2013). Such distribution likely reflects a combination of the relatively patchy outcropping along the surface of Bradbury Rise, a relatively thin stratigraphic succession within Yellowknife Bay (<7 m; Stack et al (2013a)), and ubiquitous dust coverage (commonly clumped into 60-120 lm aggregates;…”

“…cf., Sullivan et al (2008) only the larger size fractions are resolvable in MAHLI images (Minitti et al, 2013). Similarly, coarser sand-sized particles comprise a variety of dark gray to gray-white, well-rounded grains, but distinctly not spherical.…”

“…Impact spheroids are the form that can most reliably be identified by their shape and surface texture (Yingst et al, 2013;Minitti et al, 2013). Within Gale crater stratigraphy, no discrete horizons of spherules have yet been identified.…”

MAHLI on Mars: lessons learned operating a geoscience camera on a landed payload robotic arm

“…examination of eolian sand deposits, which informed a global understanding of fundamental properties and processes of eolian transport and bedform stabilization when compared to similar features at other Mars rover sites (e.g., Minitti et al, 2013;Sullivan et al, 2014;Fig. 4); 3. images for the robotic arm engineers to make lateral adjustments, based on a contextual-resolution MAHLI image acquired on a prior sol , and quantitative measurements to support placement of the rover's Alpha-Proton X-ray Spectrometer (APXS), drill and scoop (Fig.…”

JMSS-1: a new Martian soil simulant

“…However, there are also regional and trace components in Martian soil, such as carbonate, chlorohydrocarbon, and glassy spherules identified at the Gale Crater (Blake et al 2013;Leshin et al 2013;Minitti et al 2013). In situ measurements of soil samples indicate that Martian soil contains approximately 43-45 wt% SiO 2 , 16-20 wt% FeO, 7-10 wt% Al 2 O 3 , 6-9 wt% MgO, 6-8 wt% CaO, 0.7-0.9 wt% P 2 O 5 , and 5-8 wt% SO 3 (Banin et al 1992;Foley et al 2003;Gellert et al 2004;Rieder et al 2004;Blake et al 2013).…”