Mathematics – Logic
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmep51c0606f&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #EP51C-0606
Mathematics
Logic
[5416] Planetary Sciences: Solid Surface Planets / Glaciation, [5419] Planetary Sciences: Solid Surface Planets / Hydrology And Fluvial Processes, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
We present new observations of small valleys associated with glacial features in the Martian mid-latitudes, based on a survey of images from the Context Camera (CTX) on the Mars Reconnaissance Orbiter. These valleys are small (~50-400 m wide) and short (<~10 km in length); indeed, the small-scale of these valleys appears to have hindered earlier recognition. The valleys usually are adjacent to probable glacial landforms (lobate debris aprons, lineated valley fill, concentric crater fill and viscous flow features); the mechanism most likely to explain their origin is top-down melting of these cold-based glaciers. Some valleys have associated sedimentary deposits (small fans) (e.g., Fig. 1). Both stratigraphic relations and crater counting constrain most such valleys to the Amazonian period.
The observed glaciofluvial valleys are typically on slopes of <<10°, which makes them morphologically distinct from young Mars gullies, which form only on steep slopes (~15-30°). These features are also qualitatively different from valley networks that date from the Noachian/Early Hesperian, as these larger valley systems were integrated into networks that were up to hundreds or thousands of kilometers in extent. Thus, we interpret these small glaciofluvial valleys as representing a distinct class of fluvial features on Mars. Their presence shows that the hydrology of Amazonian Mars is more diverse than previously thought. Figure 1. A small valley emanating from concentric crater fill (interpreted as glacial / ice-rich) inside a 70-km crater (352.5°E, 41.5°S; CTX image P16_007256_1383). The valley begins in a small alcove, where remnant glacial materials are now ~1 km from the valley head. The valley is ~5.5 km long, has an average slope of 5°, and terminates in an elongate fan.
Dickson James
Fassett Caleb
Head James W.
Levy Jacob S.
Marchant David R.
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