Distinct small-scale (0.1 to 1 m) regolith features suggest regolith activity and provide clues about the bedrock at Glen Torridon, Gale Crater, Mars
Abstract
Glen Torridon (GT), a shallow valley in Gale Crater, Mars, is underlain by a clay-bearing unit (CBU) that was initially recognized by orbital spectroscopy and represents one of the prime motivations for landing the Mars Science Laboratory (MSL) rover in Gale Crater. While approaching and reaching GT, rover images revealed surface patterns with conspicuous regolith troughs and ridges that were better developed than those seen earlier in the mission. Their abundance and distinct character at GT naturally raise questions about whether current surface/near-subsurface processes might be responsible for their formation.
The striking surface features at GT occur in thin regolith either as shallow troughs around relatively flat-lying bedrock blocks or slabs, or as incomplete networks of ridges and troughs closely aligned with underlying bedrock fractures. The appearance, size, and texture of the GT ridges and troughs seem to resemble polygonal patterned ground found in terrestrial permafrost regions, where recurrent thermal contraction and expansion result in distinct geometric networks. At GT, however, they lack its continuity and geometric order. The exceptional development of linear regolith features in the GT region, and their close association with bedrock structures, suggest a connection with the Clay-rich nature of the bedrock. A simple assumption would be that the surface features at GT arise much as they do on earth, due to recurrent volumetric variations of the substrate driven by the large cyclic environmental changes at Gale Crater. This assumption is consistent with the surface features at GT where MSL instruments have documented unusually elevated contents of minerals known to contract and expand substantially with environmental changes: CheMin XRD results from GT document the most clay-mineral-rich samples analyzed by MSL to date, as well as the occurrence of smectites and Ca-sulfates (Bristow et al. 2019). Moreover, similar regolith features have been recognized along the MSL traverse before reaching GT, supporting the recent suggestion that GT-like mudstone was also encountered before reaching GT. Herein, we illustrate and describe the GT surface features with MSL data to help understand their formation and potential clues for bedrock interpretation.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P31A3429S
- Keywords:
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- 5215 Origin of life;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5470 Surface materials and properties;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS