Oded Aharonson
Caltech
Department of Planteary Sciences

"Granular avalanches on Mars: the dust cycle and potential role of water"

          
Abstract:

An extensive survey of Mars Orbiter Camera narrow angle images reveals
over a thousand images containing features known as slope-streaks
which are usually attributed to dust avalanches.  They represent one
of only few known examples of contemporary surface changes.  New
occurrences of streaks in overlapping images indicate these features
are currently forming at a high rate of ~7% per existing streak, per
martian year. There is either a complete turn-over within a few
decades or the streak population is currently increasing rapidly.
Gradual or stochastic variations in the dust deposition regime may be
needed to explain observations of changes in the formation rate, and
its current imbalance with the fading rate.  Correlations of slope
streak occurrence with surface properties, including thermal inertia,
roughness, and peak temperature, suggest a temperature dependent
trigger that may involve trace amounts of water undergoing phase
transition or adsorption/desorption cycles. A newly discovered,
morphologically distinct, class of massive avalanche scars are
compared with laboratory experiments in granular flow, and are used to
probe the near-surface stratification of the regolith.