Survey of remnant seasonal water ice patches at southern polar Mars

TL;DR

This survey analyzes high-resolution images of southern polar Mars to identify small residual ice patches, assessing their characteristics and potential for liquid water formation through modeling, concluding macroscopic melting is unlikely.

Contribution

It provides the first comprehensive analysis of remnant seasonal water ice patches in the southern polar region of Mars using HiRISE images and climate modeling.

Findings

148 images with small ice patches identified

Ice patches remain for 19-133 Martian days

Average noon temperature below melting point of water

Abstract

On Mars it is possible that after the recession of the seasonal polar ice cap, small icy patches left behind in shady places due to the low thermal conductivity of the Martian surface and atmosphere, are met by direct sunlight during the summer. These patches might warm up substantially and we analyzed below how could a liquid phase emerge in these places, surveying HiRISE images. 730 images that fit the selection criteria of location and season were analyzed, and we identified 148 images with smaller ice patches on them. Their separation from other bright patches, like clouds or lighter shades of layers and rocks were possible by their bluish color and strong connection to local topographic shading. These areas range between 140{\deg} and 200{\deg} solar longitude in the latitude band between -40{\deg} and -60{\deg}. The diameter of the ice patches ranges between 1.5-300 meters, and they remain on the surface even after the seasonal polar cap has passed over the area for the duration range of 19-133 martian days. With the help of The Mars Climate Database (MCD) we simulated the surface temperature and predicted CO2 and H2O ice cover at 22 analyzed areas. Judging by the models, the average noon temperature does not reach the melting point of water, which is 273 K, therefore the occurrence of liquid water on the macroscopic scale is highly unlikely, however there is a possibility that an interfacial premelting of ice (a few nanometers thick waterlayer) might form between the layered and the water ice.