Other
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p34a..01g&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P34A-01
Other
5419 Hydrology And Fluvial Processes, 6225 Mars
Scientific paper
Instruments on the Mars Reconnaissance Orbiter are providing new perspectives on fluvial processes on Mars. As the various datasets have started to mature, we are able to begin to synthesize data from multiple instruments to gain unified insights into the fluvial history of the planet. I will focus on the synthesis of CTX, HiRISE, and CRISM data at several high interest regions on the planet. Both CTX and HiRISE images reveal that post-formation processes heavily modify the valley networks and outflow channels. Although erosional features are present in some, channel bedforms and deposits are largely absent. Many valleys and channels (as well as surrounding impact craters) are filled by aeolian transported material, as indicated by the formation of dunes along the floors of these fluvial landforms. The valley networks and channels themselves may have provided an additional source material for the fine-grained infill material. Dunes are frequently found on the floors of valleys and channels, but often not on the adjacent surrounding plains. One possibility is that fine-grained material forming these dunes may be a combination of aeolian infill and reworked fluvial deposits. Another high priority target for the MRO instruments has been the intriguing, relatively young gully features. While HiRISE has sampled a variety of gully types around the planet, we have focused on a few study areas to systematically understand gully formation in a single environment. One of these study areas is the Noachis ring trough (or eroded pit crater) in the southern highlands (47S, 5E). Gullies are located around much of the perimeter of the ring-shaped depression as well as along the interior walls of the central plateau and within the innermost central pit. Debris aprons from those gullies found along the walls of the central pit overlap and coalesce on the floor. Channel forms are located on the debris aprons. Generally at Noachis, north-facing slopes exhibit light-toned layers near the gully source regions at the top of the gullied slopes. Bright deposits are also seen along some debris fans. South-facing slopes seem to lack these light-toned layers along the upper walls and instead gullies seemed to have formed on jumbled, bouldery slopes. In fact, a sharp divide formed by a small crater intersecting the larger trough feature on the east side of Noachis shows a similar relation with light-toned layers on the gullied north-facing slope and a jumbled, bouldery, undercut gullied slope on the south-facing wall. Light-tone layers are again absent along the south-facing wall. CTX images also support the observation of light-toned layers on the upper north- facing slopes. This suggests that while slope aspect does not seem to control the actual formation of gullies, it does appear to affect the morphology as well as the presence or absence of the light-toned deposits. HiRISE images do show that frosts tend to remain longer on the poleward facing slopes and CRISM data do confirm the present of CO2 and water-ice frost in these regions which perhaps may contribute to the accelerated breakdown of the light-toned deposits on the poleward (south) facing slopes.
Davatzes Alix K.
Gulick Virginia
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