Martian Seasonal Frost and Snowfall in the Northern Mid-Latitudes – Growing the Seasonal Frost Cap and Contributing Environmental Factors

Abstract:

Every year, during the Martian fall and winter, the CO₂-rich atmosphere cools in the polar and mid-latitude regions and accumulates as CO₂ frost/ ice on the surface via frost condensation and snowfall processes. This forms Mars’ seasonal frost cap. As fall progresses to winter, the maximum extent of the seasonal cap expands from the poles to the mid-latitudes, before receding back to the poles in the spring. Previous works have tracked the advance and recession of the seasonal cap edge while other studies have recorded snowfall events in the polar regions. In this study, we investigate the contribution of snowfall to the seasonal cap throughout the northern mid-latitudes. We also investigate interannual variability of the timing and spatial extent of frost and snowfall coverage and discuss several environmental factors that may contribute to the growth of the seasonal cap in the northern mid-latitudes of Mars. In this work, we primarily use Surface Brightness Temperature (SBT) data from the Mars Reconnaissance Orbiter’s (MRO’s) Mars Climate Sounder (MCS) instrument to detect surface frost and snowfall. This dataset spans ~6.5 Mars years, from MY 28-35 and contains 30,000+ observations of surface frost/ ice within the northern mid-latitudes. Preliminary results have identified several regions of the northern mid-latitudes with consistently higher frequency of frost and snowfall observations, which suggests regional-scale differences in the accumulation of both frost and snowfall. If confirmed, this new information about Mars’ seasonal volatile distribution could provide insight into seasonal cap growth/ recession. Additionally, as the seasonal frost/ ice is hypothesized to serve as an important present-day geomorphic agent, it would provide new environmental constraints for studies of seasonally-active landforms.