Subsurface Sediment Mobilization in the Southern Chryse Planitia on Mars

Abstract

AbstractThe southern part of the smooth plain of Chryse Planitia on Mars hosts a large population of kilometer‐sized (from ~0.2 to ~20 km) landforms spread over a wide area. Based on the investigation of a small part of this area, Komatsu et al. (2016, https://doi.org/10.1016/j.icarus.2015.12.032) proposed that the edifices may be the result of the subsurface sediment mobilization. We mapped the full extent of these landforms within Chryse Planitia and performed a morphological and spatial analysis in an attempt to further test this hypothesis. We identified a total number of 1,318 of these objects, which we grouped into five different morphological classes. The edifices can be observed over an area of 700,000 km2 near the termini of the large outflow channels, Ares, Simud, and Tiu Valles, with a nonrandom spatial distribution. The features are clustered and anticorrelated to the ancient highlands, which form erosional remnants shaped by the outflow events. This suggests a genetic link between the distribution of the edifices and the presence of the sedimentary deposits on which they are superposed. Such distribution is consistent with the previous notion that subsurface sediment mobilization may be the mechanism for their formation and is less consistent with the alternative igneous volcanic hypothesis. We also propose a scenario in which the large morphologic variability can be explained by variations of the water content within the ascending mud and by variations in the effusion rates. The edifices may represent one of the most prominent fields of sedimentary volcanism detected on Mars.