Mathematics – Logic
Scientific paper
May 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agusm.p32b..06s&link_type=abstract
American Geophysical Union, Spring Meeting 2002, abstract #P32B-06
Mathematics
Logic
5415 Erosion And Weathering, 5470 Surface Materials And Properties, 6225 Mars
Scientific paper
Narrow, fan-shaped dark streaks on steep slopes distributed across the brighter, low thermal inertia regions of Mars represent one of the most widespread and easily recognized styles of mass-movement currently affecting the Martian surface. The explanation most consistent with the geomorphologic evidence in MOC images is that dark slope streaks are scars from dust avalanches following oversteepening of air fall deposits[1], analogous to terrestrial avalanches of oversteepened dry, loose snow that produce shallow avalanche scars with similar morphologies. The dust avalanche process has been numerically modeled using MOLA profiles for inputs where these occur in close proximity to the avalanche scars. Contrary to the situation in terrestrial dry snow avalanches, substantial accumulations of material are not observed at the distal ends of Martian slope streaks. However, compared with snow, Martian dust particles should disperse more readily into atmospheric suspension from a turbulent avalanche mass moving even at low speed. After initiation, the sliding mass accelerates downslope and entrains more air fall dust material in a widening front. As mass and speed of the avalanche front increase, a growing fraction of the avalanching dust particles has sufficient kinetic energy to be lost to the atmosphere in suspension. Loss rate from the avalanche front to the atmosphere increases with increasing speed, until this loss rate equals the rate of mass gained by entrainment. Numerical modeling indicates these effects limit the mass and speed (momentum) of the advancing front, and result in most (typically 90+ percent) of the dust involved in the avalanche being released to the atmosphere, with very little material accumulating in distal deposits. As expected, air fall thickness and coefficients of dynamic and static friction have the greatest influence on ultimate streak length, and adjustment of these parameters is most effective for matching simulated avalanche path lengths with the actual streak lengths in the MOC images. A feature of the code is that frictional properties can also be input as a combination of cohesion and internal friction, instead of frictional coefficients, for comparisons to terrestrial material properties. However, cohesion values that lead to consistency with actual streak lengths are so low (consistent with an air fall origin) that the validity of coupled angles of internal friction is uncertain. [1] Sullivan et al. (2001) J. Geophys. Res., 106, E10, 23607-23633.
No associations
LandOfFree
Martian Dark Slope Streaks: Modeling Avalanches of Air Fall Dust does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Martian Dark Slope Streaks: Modeling Avalanches of Air Fall Dust, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Martian Dark Slope Streaks: Modeling Avalanches of Air Fall Dust will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1721821