Thermomechanical Properties of the Shallow Martian Regolith
Abstract
The seismometer placed on the surface of Mars by the InSight mission recorded signals associated with partial solar eclipses by Phobos. These signals are consistent with tilts of the seismometer. Efforts to model these tilts as a thermoelastic response to a thin (0.5-1.0 mm) layer cooling during the eclipse have shown that one way to achieve the observed tilts is to have a near-surface layer of enhanced rigidity. Another way is to have a local inhomogeneity (perhaps a buried rock) that couples the local strain field into tilts. Observations of the vertical walls of pits formed by the descent rocket blast, and around the Heat-flow and Physical Properties Probe, indicate a near-surface layer that has high cohesion that is at least several cm thick. Geologically, these steep walls with high cohesion are interpreted as duricrust which forms in sediments where small amounts of water from the atmosphere create Sulphur and Chlorine salts, depositing them at grain boundaries, weakly cementing the grains together. If we interpret the tilts during the eclipse as a response to the duricrust, we can place constraints on the relative contrast in the rigidity between the duricrust layer and the sediments below, or the thickness of the duricrust. We present an exploration of this parameter space.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP058...03H
- Keywords:
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- 0406 Astrobiology and extraterrestrial materials;
- BIOGEOSCIENCES;
- 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6297 Instruments and techniques;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS