GLOBAL AND LOCALIZED STUDIES OF CRATER DEGRADATION ON MARS

Mars has been actively changing throughout its history, and the evidence of change is preserved in the geologic features engraved on its surface. Previous studies suggest the possibility of persistent liquid water on the surface of Mars during its early climatic history. The study of impact craters can be used as a powerful tool in analyzing the Martian geologic and climatic history, as craters excavate the subsurface stratigraphy and can serve as basins for water storage. The degradation of an impact crater is indicative of erosional modification the crater has experienced since its formation. Several mechanisms for degradation include lacustrine, fluvial, aeolian, tectonic, volcanic infill, and mass wasting. Two parallel studies, one a global analysis of craters greater than 100km in diameter, and a second localized study of craters greater than 20km in the 4.1 x 10⁶ km² region to the southeast of Isidis Planitia demonstrate several important findings: (1) Both show an overall reduction in the range of Depth/diameter (D/d) with younger age units, as expected; however, (2) outlier units, with more craters displaying increased degradation indicative of greater erosion rates, are apparent in higher resolution focused study, which includes smaller craters. Ongoing work is focused on characterizing the dominant mechanism of degradation in the different units to look at changes in weathering processes through time.