HR: 14:10h
AN: P23D-03 INVITED    [Abstracts]
TI: Current and Past Aeolian Processes as Seen by the HiRISE Camera
AU: * Bridges, N T
EM: nathan.bridges@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-501 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Geissler, P E
EM: pgeissler@usgs.gov
AF: U.S. Geological Survey, U. S. Geological Survey Astrogeology Team, Flagstaff, AZ 86001, United States
AU: Team, H
EM: mcewen@jupiter.lpl.Arizona.EDU
AF: University of Arizona, Lunar and Planetary Lab 1541 E. University Blvd., Tuscon, AZ 85721-0063, United States
AB: With more than a year of observations and almost 3000 images, the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) has provided unprecedented details of aeolian features that give insight into current and past processes on the planet. Major finding include: 1) Bedform texture and relation to current sand movement: Dunes and ripples generally have superposed bedforms of smaller scale, as is commonly seen on Earth. These are visible down to the 3rd order (bedforms upon bedforms upon bedforms). Mapping of wind tails seen in the lee of rocks and, at the MER Spirit site, ventifact facets and textures, shows a co-alignment with the 2nd order, not 1st order, bedforms. This implies that recent or high energy wind activity is confined to directions orthogonal to the 1st order in these cases, probably because the major bedforms are relatively immobile due to cohesion or surface granule lags and also act to funnel near surface winds in the 2nd order direction. 2) Young bedforms: Many "young" features such as gullies and some (but not all) fresh craters contain bedforms, indicating fairly recent wind modification of the surface. 3) Bedforms in high elevation and low thermal inertia surfaces: The mantled surfaces of the Martian volcanoes (except Albor Tholus) display meter-scale reticulate ridges that probably formed from multi-directional winds. The reticulate ridges are clustered in sets at the ~20 m scale bordered by larger ridges clustered at the ~50 m scale. The larger-scale clusters may represent topography of an underlying cratered surface. The reticulate texture is generally confined to areas of thermal inertias less than 100 J/m²/K/s⁰.5, consistent with dust. How such material would be mobilized under the very low pressure (<1 to 2 mb) conditions is unknown. 4) Active sand migration at Victoria Crater: At the current site of the MER Opportunity rover, HiRISE sees a clear association between dark wind streaks extending northward from Victoria and bedforms within adjacent crater alcoves, suggesting a depositional origin for the streaks. HiRISE is continuing a monitoring campaign to assess changes in the bedforms and streaks over time
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting