SHALLOW-MARINE IMPACT CRATER CANDIDATES ON MARS

This study utilizes relatively recent imagery and altimetry data gathered by Mars Global Surveyor and Mars Odyssey to analyze the general topography and morphology of impact craters on the Martian surface. The focus is on the identification of possible shallow-marine impact craters in the region of Arabia Terra - a large area on the geologic boundary between the northern lowlands and the southern highlands that has been interpreted by some as an ancient continental shelf. If oceans existed on Mars, the large continental shelf area should display numerous shallow-marine craters. The aim of this project is to list, describe, and potentially classify, shallow-marine impact crater candidates on Mars.

A database of shallow-marine impact crater candidates, from the region 20º-40ºN and between 20ºW and 20ºE of the meridian, is being developed. For each candidate, this database lists physical crater parameters such as depths and diameters, as well as all features indicating possible shallow-marine impact conditions. Craters are then rated according to the weight of the various features observed, and a value of confidence is assigned to each of the candidates.

Some important characteristics that are associated with impact craters formed in shallow-marine environments are resurge gullies, as well as collapsed rims and features of wet mass movement, and to a lesser extent, subdued topography and central terraces. Most of these characteristics are generally visible on high-resolution images and can thus be used as key points in the identification of shallow-marine impact craters. Further distinctive attributes of these craters include the extent, shape and thickness of the ejecta deposits, as well as the volume of the crater depression and other physical parameters.

Given that the analysis of shallow-marine impact craters on Mars is still in its early stage, the results of this study are useful in the classification and characterization of these craters on a general level.