(See description below)
Streaks on Mars' Surface
This image from the HiRise
camera on the Mars
Reconnaissance Orbiter shows a portion of the wall
(light-toned material) and floor of a trough in the Acheron Fossae region of
Mars.
Many dark and light-toned slope streaks are visible on the wall of the trough
surrounded by dunes. Slope streak formation is among the few known processes
currently active on Mars. While the mechanism of formation and triggering is
debated, they are most commonly believed to form by down-slope movement of
extremely dry sand or very fine-grained dust in an almost fluid-like manner
(analogous to a terrestrial snow avalanche) exposing darker underlying material.
Some of the slope streaks show evidence that downslope movement is being
diverted around obstacles, such as large boulders, and a few appear to originate
at boulders or clumps of rocky material. These slope streaks, as well as others
on the planet, do not have deposits of displaced material at their downslope
ends. The darkest slope streaks are youngest and can be seen to cross cut and
lie on top of the older and lighter-toned streaks. The lighter-toned streaks are
believed to be dark streaks that are lightening with time as new dust is
deposited on their surface.