Use of the IMPACT Program for Measurement of the Depth to Diameter Relationships of Craters in the High Latitudes (70°–80°) of Mars: Implications for Geologic History of those Areas:

Introduction: As a practical test of the IMPACT program [1] automated method of measuring crater geometry, we have been exploring its use for studying the degradation history of impact craters in the polar regions of Mars. These regions hold important clues to the geologic and climate history of Mars, because this is where most of the volatiles are expected to occur. As an extension of our previous work in the northern high-latitudes of Mars, we have collected depth (d) and diameter (D) data for 460 craters in two regions in the southern high latitude (70°-80°S), Thyles and Prometheus. Both of these regions are Noachian age. The d/D data collected in these areas are compared with similar data for craters in the Hesperian age northern lowland plains from 70°-80°N (centered on about latitude 325°E) in order to search for signs of geologic processes. The latitudinal limits of the regions studied are equatorward of the latitudes where image data from Viking, MGS and MO reveal thick deposits fill craters and mantle the polar regions. In addition, for comparison purposes, similar data have been collected for craters on the Hesperian age ridged plains in Sinai Planum. The craters in this area exhibit sharp morphologies and show no signs of being mantled or severely eroded.