Impact Crater Deposits in the Martian Highlands

摘要

The martian highlands of Noachis Terra (20-30 deg S, 20-50 deg E), Tyrrhena Terra (0-30 deg S, 50-100 deg E) and Terra Cimmeria (0-60 deg S, 120-170 deg E) preserve long and complex histories of degradation, but the relative effects of such factors as fluvial, eolian, and mass wasting processes have not been well constrained. The effects of this degradation are best observed on large (D>10 km) impact craters that characterize the ancient highlands. Some craters exhibit distinct interior deposits, but precise origins of these deposits are enigmatic; infilling may occur by sedimentary (e.g., fluvial, lacustrine, eolian), mass wasting and (or) volcanic processes. Analysis of Viking, MOC, THEMIS, MOLA, and TES data are allowing detailed characterizations of impact crater morphologies, geologies, erosional and depositional histories, and ages to be determined. This study intends to (1) characterize the complex geologic and geomorphic terrains found within highland craters, (2) determine the origin(s) and ages of floor deposits, and (3) investigate degradation processes that might have affected impact craters in these regions. Several studies have suggested that large impact craters on Mars may have contained standing bodies of water that could have been ideal environments for life to persist. Determining the nature of impact interior deposits will provide targets for future landing sites in order to identify sources of subsurface water as well as evaluate evidence for biologic activity.