THE DEGRADATION OF IMPACT CRATERS IN MAJA-VALLES AND ARABIA, MARS

Photoclinometry is being utilized to quantify the degree of degradation suffered by Martian impact craters (1- to 5-km-diameter range) in the Arabia and Maja Valles regions. Results indicate that present crater depths can vary substantially from crater depths expected for the original fresh craters at all sizes examined. Localized regions of high, moderate, and low degradation of the order of 10(2) km(2) have been delineated using the percentage change in crater depth/diameter between current and assumed fresh crater morphology. Regions of low degradation occur randomly across these regions and probably represent recently produced impact craters which have undergone little degradation since their formation. Aeolian activity, including current mantling deposits, appears to dominate the processes degrading craters in the Arabia region, with fluvial and impact processes playing a secondary role. In the Maja Valles region, crater degradation is associated primarily with fluvial outflow channel activity, with aeolian and impact processes contributing secondary effects to the destruction of impact craters.