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Date Entered: 31 October 1989
Date Last Revised: 5 November1993
The site lies at a contact between ancient cratered terrain and ridged plains materials that are probably flood lavas of intermediate age. Plains materials lap up against the higher cratered terrain at the contact. A number of well-developed ancient valley systems are present in the cratered terrain and debouch at the contact. The valleys apparently predate emplacement of the plains materials. The geometry of the valleys is not clearly confluent, so it is not clear that fluvial sediments underlie the plains materials. Fresh craters up to about 10 km in diameter excavate into the plains materials, and there are a few ancient buried craters whose rims protrude upward through plains materials.
Scientific Rationale
To be determined.
Objectives
Ancient cratered terrain, recent volcanics.
Potential Problems
To be determined.
Trafficability
To be determined.
Estimated Traverse Distance
To be determined.
Exobiology Significance
The plains materials occupy a depression that may have been a lacustrine depocenter for the sorrounding drainage basins. The presence of higher order tributaries and incised meanders in the upper reaches of some of the more prominent channels suggest a prolonged period of hydrologic activity.
Sampling the subsurface basinal materials is of particular interest to Exobiology because, if lake sediments are present, they may provide a record of long term hydrologic history, and possibly, a fossil record. Applying predictions from simple facies models, deposits in the central region of a lacustrine basin are expected to include fine-grained detrital sediments (e.g. shales) and perhaps evaporites.
Such lithologies often favor preservation of organic matter. Under appropriate geohydrological conditions, coarser-grained marginal facies are often a locus for carbonate mineralization, which also enhances the potential for fossilization and the preservation of organic compounds.
Given that the younger plains units covering the basin floor are probably volcanic, the proposed landing target is located on the distal ejecta blanket of an ~40 km diameter crater. In the absence of drilling, crater ejecta probably offers the best opportunity to obtain samples of the subsurface deposits which underlie the ridged plains unit. That is the reason why the proposed exobiology target is located at 37 deg. S, 230 deg. W.
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