Examining the sediments and soils of Gusev Crater with the Athena science payload

Abstract

[1] Gusev Crater has been proposed to contain lacustrine and/or fluvial sediments; however, eolian or volcanic sediments, global dust, and locally produced soils may also be present. This work describes the use of the Athena instrument package to evaluate the environment in which sampled materials were deposited in Gusev Crater. Sedimentary or soil deposits can be sampled by examining materials that were (1) excavated by impact events, (2) revealed by wind deflation, or (3) exposed by spinning the rover wheels. Specific observations can be diagnostic of a depositional environment. For instance, Pancam images of thin (e.g., 5 cm) planar layers of phyllosilicates and/or evaporites (as determined by Mini-TES) would suggest lacustrine sediments. Layered sediments (e.g., trough cross bed) with rounded particles (>4 mm) would suggest fluvial activity. Eolian sediments may have planar or cross-planar layers of well-sorted grains ($200 mm). Parallel bed deposits consisting of glass observable by Microscopic Imager would indicate volcanic ash. Soil bulk chemistry reported by Alpha Particle X-ray Spectrometer that is similar to the Viking and Mars Pathfinder soils would indicate global dust. Mini-TES should only detect primary mineralogies in physically weathered soils, whereas chemically weathered soils may contain carbonates, sulfates, and/or phyllosilicates. Although some characteristics are unique to a sediment or soil deposit, different deposit types can have similar characteristics (e.g., planar layering). Determining the depositional history of material in Gusev will require the integration of measurements from several instruments and careful geologic reasoning by the investigators.

A volcanic interpretation of Gusev Crater surface materials from thermophysical, spectral, and morphological evidence

“…An alternative explanation is that the ejecta materials have higher thermal inertia because of their coarser particle size, maybe due to reduction of fines. Regolith formation may be due to physical weathering of basaltic materials by processes such as wind abrasion, thermal cycling, freeze thaw of interstitial water in cracks [ Sutter et al , 2004], and impact cratering.…”