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G. Komatsu, A.P. Rossi (IRSPS, Universita' d'Annunzio, Pescara, Italy), J.S. Kargel (Astrogeology Team, USGS, Flagsatff, Arizona, U.S.A.)
We examined recent MOC images to assess the glaciation hypothesis on Mars. The MOC high resolution images of Hellas basin, although limited in coverage, reveal a range of erosional landforms which we interpret to be scoured by glacier movement. The landforms include widespread striations, grooves, and roche mountonnée. Formation of these features by other possible erosional agents, such as wind, as suggested by others, is also possible (e.g., Moore and Edgett, 1993). The inferred flow directions from these landforms are consistent with the regional topography and ice sheet reconstructed by Kargel and Strom (1992), but also might have been formed by downslope wind. MOC coverage of the Argyre basin is even more limited, but one sequence shows at high resolution features that suggest fluvial erosion/deposition in a sourceless braided channel network, which possibly is the product of subglacial fluvial action or proglacial outwash as previously suggested by Kargel and Strom (1992). Huge boulders present in this fluvial landscape support glacial or glaciofluvial processes of a high-energy, short-term (catastrophic) nature similar to the high-magnitude transient water outflows common among wet-based ice sheets and glaciers on Earth. We also identified flow-like features on the flanks of canyon walls of Valles Marineris and fretted channels near the highland/lowland dichotomy boundary. Impact craters on these flows-like features in Valles Marineris are deformed along the direction of the flows. We hypothesize that the flows either contain a large amount of interstitial ice or are ice-cored. The numbers of undeformed impact craters on the flows in Valles Marineris and fretted channels are very small, indicating that the flows may have been active until recently or are still active in some cases.
The author(s) of this abstract have provided an email address for comments about the abstract: goro@sci.unich.it