Recent Spirit Rover Results: Morphological and Textural Analysis of Sulfate-Rich Soils to the West of Home Plate
Abstract
The Mars Exploration Rover Spirit is sitting on the upper eastern wall of an ~8 m wide, shallow circular depression located to the west of Home Plate. The rover has a 12 degree roll to the west, with the left wheels within the crater and the right wheels on a plateau to the east of the crater. The region is called “Troy”, and an extensive campaign of observations has been conducted of the disturbed soil (“Ulysses”) and two surfaces on the plateau (“Cyclops Eye” and “Polyphemus Eye”). The campaign included extensive measurements in Ulysses by the Panoramic Camera and Alpha Particle X-Ray and Mössbauer Spectrometers. In addition, the Rock Abrasion Tool (RAT) was used to excavate into the “Eye” Targets with subsequent measurements using the science payload. The data show that the Ulysses soils are dominated by sulfate-rich materials, mixed with varying amounts of basaltic sand and silt. The compositional and mineralogical observations were accompanied by images taken by the Microscopic Imager (MI), a fixed-focus camera with 31micrometer/pixel image scale. Particle size distributions derived from MI images show that the Ulysses soils are composed primarily of fine to medium sized sand grains, with some agglomerates and a component of silt grains below the resolution of the instrument (~0.1 mm). A comparison of the 2D perimeter and cross-sectional areas of the particles indicates that the soil is dominated by angular fragmented particles. The angularity indicates that this soil is local in origin. Surface soils on the plateau to the east of Ulysses are composed of well-sorted, round, fine basaltic sand, likely sorted by aeolian transport. The deepest soil uncovered by the RAT at Cyclops Eye (~10 cm to east of Ulysses) shows a mix of angular sulfate-dominated grains, and round basaltic particles. On the other hand, materials on the surface and those exposed in Polyphemus Eye (~30 cm to east of Cyclops Eye) indicate the presence of basaltic materials with only modest enrichments in sulfate-bearing particles. Results are consistent with a local occurrence of the sulfate-rich soils within the shallow circular depression, perhaps as aeolian infill of locally-derived hydrothermal deposits or as an in-situ hydrothermal deposit.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.P13A1250S
- Keywords:
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- 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS