Abstract
The southern part of the smooth plain of Chryse Planitia on Mars hosts a large population of kilometer-sized (from similar to 0.2 to similar to 20km) landforms spread over a wide area. Based on the investigation of a small part of this area, Komatsu et al. (2016, ) 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 700,000km(2) 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.
Plain language summary Ever since the presence of methane in the Martian atmosphere was reported from ground-based, orbital, and in situ observations, mud volcanism was hypothesized to be a possible release mechanism, and various mud volcano fields have been tentatively identified. Although morphological similarities with Earth sedimentary volcanism have been proposed (e.g., Skinner & Mazzini, 2009, ), it is difficult, however, to prove unambiguously the presence of mud volcanism in remote sensing data, and some of the reported mud volcanoes have alternatively been interpreted as igneous volcanoes.
A definitive identification of sedimentary volcanoes on Mars is therefore still problematic. A useful candidate area to test the hypothesis of sedimentary volcanism on Mars is a field of kilometer-sized cone- and pie-like landforms in the southern part of the large ancient Chryse impact basin, part of which was previously studied by Komatsu et al. (2016, ).
In this study, we searched for those landforms inside Chryse Planitia and determined their full spatial extent. We found that they can be divided into five morphologically different groups and that they occur exclusively on the level sedimentary plains.
These findings enable us providing additional evidence to support the hypothesis of subsurface sediment mobilization as a possible mechanism for their formation.