Large-scale lava-ice interactions on Mars: Investigating its role during Late Amazonian Central Elysium Planitia volcanism and the formation of Athabasca Valles

Abstract The Central Elysium Planitia region contains evidence for large-scale, Late Amazonian volcanic and fluvial activity, the youngest on Mars. The region consists of a population of geologically recent, Late Amazonian-aged flood basalt volcanic plains which are incised by several large fluvial outflow channel systems. Recent understanding of the distribution of paleo-glaciation on Mars, informed by geomorphic indicators and model predictions, suggests that Central Elysium Planitia was an area of likely surface snow and ice accumulation throughout the Amazonian period. Furthermore, the volcanic plains of Central Elysium Planitia contain wide areas with preserved rootless cones, representing among the strongest evidence for past lava-ice interactions on Mars. Consequently, Central Elysium Planitia is of significant interest to understanding the recent Amazonian thermal and hydrologic history of Mars. Here we perform an exploratory assessment of the influence of surficial large-scale lava-ice interactions on the geomorphology of the Central Elysium Planitia volcanic plains and their potential contribution to the formation of the fluvial outflow channels contained within the region. The outflow channels of Central Elysium Planitia are generally interpreted to have formed as a result of catastrophic outbursts of groundwater released from pressurized, confined subsurface aquifers by magmatic dike emplacement. However, the formation of the relatively young Central Elysium Planitia outflow channels by this mechanism is subject to several demanding conditions which are not required of a lava-ice interaction origin. Therefore we revisit the origin of the Central Elysium Planitia outflow channels and explore large-scale lava-ice interactions as a possible alternative mechanism to contribute to, or account for, their formation. This assessment is performed through a case study of Athabasca Valles, a well-characterized outflow channel system which appears to emanate from the Cerberus Fossae fissure system. We find that surface ice and lava-ice interactions could have influenced the geomorphology of Central Elysium Planitia by contributing to the formation of the regions platy-ridged volcanic plains texture and rootless cones. Large-scale lava-ice interactions in Central Elysium Planitia are found to be able to readily supply the water volumes needed to form the Athabasca Valles system, but additional mechanisms are required to cause meltwater confinement and release to supply requisite discharges. Of the several potential mechanisms which could have led to meltwater confinement and release, the most likely are supra/englacial melt accumulation with outflow triggered by the flotation of a confining ice dam, and supra/englacial meltwater accumulation released by top-down supraglacial overflow. A simple analysis of these processes indicates that the rates of discharge necessary to form Athabasca Valles can be supplied while adhering to the geomorphic constraints of the system. Therefore, we conclude that the formation of the Athabasca Valles outflow channel system (and possibly other outflow channels in the region) could plausibly have been the result of surficial lava-ice interactions through meltwater confinement, accumulation, and release, providing an advantageous alternative to classical groundwater outburst models.