A low albedo, thin, resistant unit in Oxia Planum, Mars: evidence for an airfall deposit and late‐stage groundwater activity at the ExoMars rover landing site
Author(s)
Harris, E
Davis, JM
Grindrod, PM
Fawdon, P
Roberts, AL
Type
Journal Article
Abstract
Oxia Planum, Mars, is the future landing site of the ExoMars Rosalind Franklin rover mission, which will search for preserved biosignatures in a phyllosilicate-bearing unit. Overlying the mission-important phyllosilicate-bearing rocks is a dark, capping unit—known here as the Low albedo, Thin, Resistant (LTR) unit—which may have protected the phyllosilicate-bearing unit over geologic time from solar insolation and radiation. However, little is known about the origin of the LTR unit. Here, we map the LTR unit and investigate its distribution and morphology across 50,000 km2 using a variety of orbital remote sensing data sets. The characteristics of the LTR unit include draping palaeo-topographic surfaces, deposition over a wide elevation range, and a consistent vertical thickness that can be best explained by airfall deposition including a primary or reworked volcanic palaeo-ashfall. Previous research suggests that the LTR unit was not significantly buried, and we find it to be preferentially preserved with a high mechanical strength in discrete deposits representing palaeo-topographic lows. We suggest this could be attributed to localized cementation via upwelling groundwater. This scenario suggests that most of the phyllosilicate-bearing exposures may not have been protected over geologic time, as the uncemented LTR sediment would have easily been removed by erosion. However, our observations indicate that the scarped margins of the LTR unit deposits probably exposed regions of the once protected phyllosilicate-bearing unit. These areas could be key science targets for the ExoMars Rosalind Franklin rover mission.
Date Issued
2024-11-01
Date Acceptance
2024-11-03
Citation
Journal of Geophysical Research: Planets, 2024, 129 (11)
ISSN
2169-9097
Publisher
American Geophysical Union (AGU)
Journal / Book Title
Journal of Geophysical Research: Planets
Volume
129
Issue
11
Copyright Statement
© 2024. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
10.1029/2024JE008527
Publication Status
Published
Article Number
e2024JE008527
Date Publish Online
2024-11-22