HR: 09:45h
AN: P21C-08 INVITED    [Abstracts]
TI: From Gullies to Outflow Channels: HiRISE's Perspective on Fluvial Activity on Mars
AU: * Gulick, V C
EM: vgulick@mail.arc.nasa.gov
AF: NASA Ames Research Center/SETI Institute, M.S. 239-20, Moffett Field, CA 94035, United States
AU: team, t
AB: The Mars Reconnaissance Orbiter's High-Resolution Imaging Science Experiment (HiRISE) has imaged many putative fluvial landforms on Mars at unprecedented resolution. These targets include gullies, young valleys, outflow channels, valley networks, and large valley systems. The gullies, which may provide evidence of recent water flow on Mars, have received particular attention. We find that gullies exhibit a wide range of morphologies, sizes (varying width, lengths and depths), geologic settings, and associations with other features. This diversity challenges several of the proposed gully formation mechanisms and may suggest a diversity of origins for these landforms. HiRISE is also providing additional details of meter- and larger-scale erosional features located within the outflow channels, including layering in the walls, subchannels in the floors, and multiple headcuts within the cataract systems. Fewer HiRISE images have been taken of older features, including the valley networks, because the nearly ubiquitous Martian dust mantle (as well as other mantling and infilling material) often obscures key bedforms of interest. For example, HiRISE observations of Warrego Vallis, the textbook ancient martian valley network, are challenging to interpret as the valley floors have been partially infilled by post formation materials. However, the addition of HiRISE color and stereo data is proving useful in helping to unravel some of the mysteries associated with their formation. Finally, HiRISE has found evidence for surface runoff (e.g., gullies, dissected alluvial fans) in some pristine, mid-sized impact craters (e.g., Mojave, Hale). One possible explanation may be that these fluvial features formed from the release of volatiles or subsurface fluids, followed by localized precipitation, melting and runoff associated with impact processes. In my presentation, I will summarize the most interesting HiRISE observations of the Martian fluvial landforms, focus on evidence for recent fluvial activity, and discuss our current interpretations.
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting