SEASONAL TEMPERATURE VARIATIONS AND ALBEDO VARIATIONS FOR CO2 ICE, H2O ICE AND REGOLITH IN THE SOUTH POLAR AND NORTH POLAR REGIONS OF MARS

Martian surficial H₂O ice will be invaluable to future human and robotic exploration. Both the south and north polar regions of Mars are covered with H₂O ice deposits overlaid with seasonal CO₂ ice caps. In the southern summer the south polar region has a residual permanent CO₂ ice cap. In contrast, the northern seasonal CO₂ ice completely sublimates during northern summer.

This project investigates seasonal surface temperature and albedo variations in two Martian polar regions: an exposed H₂O ice region near the edge of the perennial south polar cap and a region of H₂O ice near the north pole with the goal of understanding the differences between regions covered with CO₂ ice, H₂O ice and regolith.

A previously discovered region of exposed H₂O ice centered around 85°S and 10°E was investigated. A north polar region centered around 85°N and 5°E close to Chasma Boreale was studied for comparison. THEMIS infrared images were analyzed using JMARS software to calculate the average surface temperatures. Albedos were calculated from the calibrated THEMIS visible images.

In the south polar exposed H₂O ice region, in early spring all three areas are covered with a continuous layer of CO₂ ice, and have the same temperature which increases from 140 K to 160 K as spring progresses into summer. After Ls 280°, the temperatures differentiate into thermally distinct units: CO₂ ice, H₂O ice, and regolith. The CO₂ ice is colder than the H₂O ice, and the regolith is warmer than both.

Albedos for the three units are similar during spring, however, after Ls 280°, they differentiate. The CO₂ ice has the highest albedo (0.60), H₂O ice has intermediate albedo (0.42), while regolith has the lowest (0.33). The exposed H₂O ice unit is identified based on its temperature and albedo. THEMIS infrared images taken in late summer reveal that the H₂O ice unit extends more than 100 km, indicating that H₂O ice is widespread around the southern perennial polar cap.

Seasonal temperature and albedo variations for H₂O ice units in the north polar region were studied during the northern spring and summer. Preliminary results yield albedo values ranging from 0.65 to 0.25 depending on the composition of the unit. These results will be compared with the seasonal variations in the south polar regions.