HR: 09:30h
AN: H31G-05    [Abstracts]
TI: Incision of Fluvial Channels on Titan
AU: * Collins, G C
EM: gcollins@wheatonma.edu
AF: Wheaton College, Physics and Astronomy Dept. 26 E. Main St., Norton, MA 02766 United States
AB: Networks of sinuous channels have been observed on the surface of Titan, most notably by the imaging experiment on the Huygens probe [1], and these channels may be carved into the icy surface by infrequent torrential downpours of liquid methane from the thick atmosphere [2]. A methane stream on Titan with water ice sediment will operate at a higher transport stage than a stream on the Earth with the same shear velocity, due to the lower gravity and increased sediment buoyancy on Titan [3]. The low gravity also requires steeper slopes or greater flow depths to achieve the same shear velocity, which cancels out part of the increased transport stage on Titan. The incision of stream channels into Titan's ice bedrock may take place by abrasion, plucking, and/or cavitation [e.g. 4]. Bedload abrasion is investigated using the Sklar and Dietrich model [5] and by measuring the abrasion resistance of water ice at near-Titan temperatures. The resulting erosion rates are similar to what would be expected in a sandstone channel on Earth, for the same values of slope, discharge, and sediment supply. Abrasion by suspended particles may scale in a similar way. Plucking could be slightly enhanced by higher transport stage in Titan streams, but the production of pluckable bedrock blocks depends on unknown ice bedrock parameters such as jointing or layering. Due to the high atmospheric pressure, cavitation is probably a slightly less effective erosive agent on Titan than on the Earth. The result of comparing fluvial incision processes on Earth and Titan is that despite orders of magnitude differences in some of the physical parameters that govern these processes on the two bodies, the erosion rates are likely to be fairly similar, given similar stream conditions. It remains to be seen whether the assumption of similar stream conditions (slope, discharge, sediment supply) is valid, and this can be addressed with further modeling and analysis of data from the Cassini-Huygens mission, as well as data that could be collected by a future Titan-focused mission. References: [1] Tomasko et al., Nature, 2005; [2] Lorenz et al., GRL, 2005; [3] Burr et al., Icarus, submitted; [4] Whipple et al., GSA Bull., 2000; [5] Sklar and Dietrich, Water Resour. Res., 2004.
DE: 5415 Erosion and weathering
DE: 5419 Hydrology and fluvial processes
DE: 6281 Titan
SC: Hydrology [H]
MN: Fall Meeting 2005