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Near Surface Stratigraphy and Regolith Production in Southwestern Elysium Planitia, Mars: Implications for Hesperian-Amazonian Terrains and the InSight Lander Mission

The presence of rocks in the ejecta of craters at the InSight landing site in southwestern Elysium Planitia indicates a strong, rock-producing unit at depth. A finer regolith above is inferred by the lack of rocks in the ejecta of 10-m-scale craters. This regolith should be penetrable by the mole of...

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Published in:Space science reviews 2017-10, Vol.211 (1-4), p.147-190
Main Authors: Warner, N. H., Golombek, M. P., Sweeney, J., Fergason, R., Kirk, R., Schwartz, C.
Format: Article
Language:English
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Summary:The presence of rocks in the ejecta of craters at the InSight landing site in southwestern Elysium Planitia indicates a strong, rock-producing unit at depth. A finer regolith above is inferred by the lack of rocks in the ejecta of 10-m-scale craters. This regolith should be penetrable by the mole of the Heat Flow and Physical Properties Package (HP 3 ). An analysis of the size-frequency distribution (SFD) of 7988 rocky ejecta craters (RECs) across four candidate landing ellipses reveals that all craters >200 m in diameter and < 750 ± 30 Ma in age have boulder-sized rocks in their ejecta. The frequency of RECs however decreases significantly below this diameter ( D ), represented by a roll-off in the SFD slope. At 30 m < D < 200 m , the slope of the cumulative SFD declines to near zero at D < 30 m . Surface modification, resolution limits, or human counting error cannot account for the magnitude of this roll-off. Rather, a significant population of 3 m by the HP 3 however increases significantly due to the increase in boulder-size rocks in the lower regolith column, near the interface of the bedrock.
ISSN:0038-6308
1572-9672
DOI:10.1007/s11214-017-0352-x