I noticed the Aharonson et al. submission a little over a month, which is when the abstracts became available online. Aharonson et al. suggest the possibility of a "wet" interpretation to the dark
slope streaks described by Rob Sullivan et al., most recently in the MGS Special Issue of JGR-Planets, as likely due to "dry" dust avalanches. In fact, Sullivan has an abstract submitted to this meeting, which I post further down.

I am interested in seeing more details of Aharonson et al.'s work, especially how they differentiate (e.g., morphologies, slope source orgins, etc.) their "wet" slope streaks at higher latitudes, where
near surface ice is thought to be stable, from the "dry" slope streaks at lower (near equatorial) latitude, low thermal inertia (dustier) sites, where the near surface is thought to be highly
dessicated.

At any rate, the most important passage from Aharonson et al., at least for me, is: "Repeat images of sites with slope streaks show changes only if surface temperatures exceeded the melting point of water during the time interval between the two images." I'd be
interested in knowing exactly how many "sites with slope streaks
[that] show[ed] changes" were documented, which is key to
understanding the correlation to *surface* temperatures, which is
what TES measured.

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16:45h
AN: P32B-06
TI: Martian Dark Slope Streaks: Modeling Avalanches of Air Fall Dust
AU: * Sullivan, R
EM: rjs33@cornell.edu
AF: CRSR/Astronomy, 308 Space Sciences Cornell University, Ithaca, NY
14853 United States
AB: 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.
DE: 5415 Erosion and weathering
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: P
MN: 2002 Spring Meeting

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Alex R. Blackwell
University of Hawaii