THE CHANGE IN MARTIAN CRATER MORPHOMETRY WITH TIME

Quantitative relationships between morphologic characteristics of impact craters (a.k.a. crater morphometry) are well-known for impact craters on most solid bodies in our solar system. However, most previous studies have utilized data sets of global crater populations, including both recently-formed and ancient impact craters. Thus our first attempts at deriving morphometric relationships encompass all or many age populations. However, little is known about how impact crater morphometry changes over geologic time spans when craters are exposed to active surficial/atmospheric processes.

Mars is geologically active planet that has a well-preserved crater population despite the fact that it has been affected by erosion and weathering processes since its earliest epoch. In this study, we have sub-divided the crater population into groups accordant withmartian geologic periods (Noachian, Hesperian, Amazonian) and have measured crater dimensions to track changes in crater morphometry over time. Eight topographic profiles were extracted for each impact crater from a 128 pixel/degree spatial resolution MOLA digital elevation model. Summary statistics have been generated for each crater which includes the mean and standard deviation for the central peak parameters, height and diameter. Preliminary results do not support systematic changes to impact crater morphometry relative to time. It is possible that geologic activity hasn’t affected morphology in a way that can be detected using an assessment of crater morphometry. A more likely scenario is that these preliminary results are limited by too small crater populations. We anticipate inclusion of remaining data will support our expectation of systematic morphologic changes across all three martian geologic epochs.