Thermophysical and Compositional Properties of Paleobedforms on Mars

Bedforms on Earth and Mars are often preserved in the rock record in the form of sedimentary rock with distinct cross‐bedding. On rare occasions, the full‐surface geometry of a bedform can be preserved through burial and lithification. These features, known as paleobedforms, are found in a variety o...

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Bibliographic Details
Published in:Journal of geophysical research. Planets 2022-08, Vol.127 (8), p.n/a
Main Authors: Weintraub, Aaron Robert, Edwards, Christopher Scott, Chojnacki, Matthew, Edgar, Lauren A., Fenton, Lori K., Piqueux, Sylvain, Gullikson, Amber L.
Format: Article
Language:English
Subjects:
Bedforms
Cement
cement volume
Dunes
Environmental conditions
Geographical locations
Lithification
lithified bedforms
Mars
Mars craters
Mars environment
Modelling
paleobedforms
paleodunes
Physical properties
River beds
Sand
Sedimentary rocks
Sedimentary structures
Specific heat
Surface geometry
Thermal inertia
Thermophysical models
Thermophysical properties
Weathering
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Summary:Bedforms on Earth and Mars are often preserved in the rock record in the form of sedimentary rock with distinct cross‐bedding. On rare occasions, the full‐surface geometry of a bedform can be preserved through burial and lithification. These features, known as paleobedforms, are found in a variety of geographic locations on Mars. Evidence in the morphology of paleobedforms, such as the retention of impact craters and steep erosional scarps, suggests that these features are well‐lithified and capable of withstanding prolonged weathering and erosion. Here, we present results from thermophysical and compositional analyses on a subset of the best preserved paleobedform candidate fields on Mars. Thermophysical modeling elucidates the changes these bedforms underwent from their unconsolidated, particulate nature to their currently observed properties. Certain paleobedforms have elevated thermal inertias (e.g., ∼300–500 J·m−2·s−1/2·K−1) when compared with modern bedforms (∼250 J·m−2·s−1/2·K−1), and modeling indicates that they have cement volumes of 0.8%–1.5% even as high as 30%. However, most paleobedform candidates have unexpectedly low thermal inertia when compared with modern dunes. Additionally, compositional analyses reveal a range of spectral characteristics within paleobedforms (e.g., primary and secondary alteration products). These features add to the already existing class of Martian surfaces in which thermal inertia does not seem to correspond to erodibility, cohesion, or mechanical strength. Studying paleobedforms with both raised and nonraised thermal inertia has provided new insights into lithification on Mars and constrained the environmental conditions leading to the formation of these enigmatic features. Plain Language Summary Mars is covered by a variety of features, such as sand dunes and ripples, referred to as bedforms. Most are composed of unconsolidated sand and are capable of migrating under contemporary winds. Some bedforms seem to have become lithified, resembling these active dunes, yet sharing traits with solid rock. These features are called paleobedforms. We study a sample of paleobedforms on Mars to understand the mechanisms that led to their formation and preservation. Their physical properties—characterized using thermal inertia—and their composition were compared to active dunes. We constrained the cement volume that may be contained within these paleobedforms based on their physical and mineralogical properties. A few sites hav
ISSN:2169-9097
2169-9100
DOI:10.1029/2022JE007345