Impacts of mesoscale meteorology on the evolution of fluvial features in Lyot crater, Mars

Abstract

Identifying possible fluvial activity during the past and near present on Mars is a key area of martian research, as the occurrence of stable surface water can be an indicator of potentially habitable locations which are of astrobiological interest. Lyot crater is an early Amazonian-aged impact crater in the northern lowlands of Mars. It has a microenvironment due to the low elevation of its interior, where fluvial features and ice-rich landforms have been identified today. We modelled the mesoscale atmospheric conditions in Lyot over the past 20 million years, as Mars’s orbital parameters changed, to identify periods in time and space where conditions were suitable for stable surface water. As well as investigating surface temperature and pressure, an assessment was also made of the impact of relative humidity and evaporation on stable surface water, and the effect of solar insolation and shadowing on the longevity of ice-rich meltwater source materials. At lower obliquities the modelled atmospheric states identify conditions when stable surface water could flow in the summer over much of the crater for a few hours per sol. At higher obliquities modelled conditions suitable for stable water were restricted to the lowest elevation areas of the crater interior. These are areas where the longest channels have been identified and are also areas where standing bodies of water may have formed as these long channels drained into topographic lows. The conditions suitable for supporting stable liquid water at the surface only occurred in the model for short periods of time, hence, an assessment was also made as to the possible behaviour of surface water during the longer intervals when conditions were not suitable. During these times surface water would have boiled or frozen, although if the depth of surface water was sufficiently deep, then a layer of ice on the surface of the water could have protected the liquid water underneath. It would then flow again when conditions were suitable and the ice cover melted or if conditions remained unsuitable the covered water feature would stagnate and disappear over time. This research supports the conclusion drawn from geomorphological analysis that stable surface water occurred in specific locations such as Lyot crater in the recent past on Mars.