Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p22a..01d&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P22A-01
Physics
[5415] Planetary Sciences: Solid Surface Planets / Erosion And Weathering, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Martian gullies on steep slopes have been the focus of much controversy in recent years, as scientists seek to understand how they develop and what they imply about the martian environment. In this study, we examine classic gullies (composed of an alcove/channel and apron) on martian dunes in the southern hemisphere which have been active during the last 4.5 martian years. We completed a general survey of MOC, CTX, and HiRISE images, and found dune gullies from 40-70S, poleward of crater gullies. We also identified periods of gully activity -- measurable changes in gully morphology and/or geomorphic signatures of recent apron deposition. Changes in 17 gullies, within 6 dune fields (latitude 45-52S), all appear to occur during the early southern spring, implying the existence of a seasonal control. These observations and timeframes are consistent with the appearance of fresh-appearing deposits in classic non-dune gullies, implying a related evolution process [1]. We hypothesize that current dune gullies’ evolution is related to seasonal accumulation of CO2 frost -- possibly by initiating shear flow by loading the surface [2] and/or increasing the fluidity of dry granular flow [3]. [1] Dundas, et al. (2009, this conference). [2] Ishii and Sasaki (2004) LPSC XXXV, abstract 1556. [3] Hugenholtz (2008) Icarus, 197:65-72. Spacecraft images showing changes in debris apron at large dune gully (49.49S, 34.86E), since 2002. In MOC E12/01043 (top image, 2002, Ls306 My 25), bright bedforms were visible at the foot of the debris apron. Those bedforms were partially covered in HiRISE PSP_006648_1300 (middle image, 2007, Ls9 My 29) and almost completely covered in HiRISE ESP_013478_1300 (bottom image, 2009, Ls283 My 29). To see the full-resolution HiRISE images, visit http://hirise.lpl.arizona.edu.
Byrne Shane
Diniega Serina
Dundas Colin Morrisey
McEwen Alfred
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