The Periglacial Landforms and Estimated Subsurface Ice Distribution in the Northern Mid-Latitude of Mars

Abstract

Subsurface ice in the mid-latitude regions is a significant water inventory on present-day Mars, and their volume and distribution are thought to have varied due to the orbitally induced paleoclimatic changes. Using high-resolution satellite images, the present study explores the distributions of three presumed periglacial landforms (thermal contraction polygons, fractured mounds, and brain terrains) that could provide evidence for the present-day subsurface ice distribution in the northern mid-latitude (30°–42°N). We identified the three periglacial landforms concentrated within the regions of 0°–40°E, 60°–100°E, and 160°–210°E in the latitude of >33°N. Their distributions are in agreement with the occurrence of fresh ice-exposing craters and the estimated area of high annual water ice budget obtained by the general circulation model, reflecting the present-day subsurface ice distribution. We further classified the thermal contraction polygons into five types based on their morphology, and investigated various distribution patterns for each type. Among them, high-centered polygons are the most abundant type in the survey area, whereas low-centered polygons are less prominent and observed only at >38°N. The large-sized mixture polygons, which were only found in certain areas of 57°–92°E, are distributed in areas where the atmospheric model indicates that the highest annual water ice budget occurred during the past high-obliquity period, but that the water ice budget has decreased during the present-day low-obliquity condition. These findings, along with insights from possible terrestrial analogs in the Arctic Archipelago and northern Canada, suggest that regions where large-sized mixture polygons formed contained significant amounts of water ice in the past, but have undergone intense degradation over time.