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Mars Dunes Mug for Camera
By Andrew Bridges
Chief Pasadena Correspondent
posted: 01:33 pm ET
02 February 2000
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mars_dunes_000202 PASADENA, Calif. - Newly released images of Mars show a wide variety of sand dunes stud its surface -- from shifting piles active in recent years to others so old they are pocked with the scars of ancient impact craters.The images, all acquired by the orbiting Mars Global Surveyor, reveal a cross section of how sand behaves on the blustery surface of Mars, where sudden storms can envelope the entire planet in a dusty veil. Scientists have known for centuries that Mars is a dusty place -- ever since astronomers first trained their telescopes on the Red Planet they've seen the clouds of debris that blow across its surface. It wasnt until the Mariner 9 spacecraft, which in the fall of 1971 became the first probe to orbit another planet, that scientists learned sand forms sometimes extensive dunes on Mars surface.Since then, the Mars Orbiter Camera (MOC) on Global Surveyor, currently in martian orbit, has broadened that view by imaging the planet in unprecedented detail.The new images, released by the MOCs builder, San Diego-based Malin Space Science Systems, show that Mars is far from static, at least when it comes to dune activity. 
Dunes in the Rabe Crater region of Mars have shifted as recently as a few months ago, spilling fresh sand down in mini-avalanches. 
In the Lycus Sulci region, the images show darker material has moved over lighter, inactive dunes, rushing down-slope and streaking the sand in a fluid-like manner. In some places, although rare, the dunes have grown almost "fossilized" -- locked in place by some unknown means. Harsh winds have then sculpted those dunes in regions like the Terra Cimmeria. There the winds scour away at the sands, leaving rough edges instead of the soft, pillowy nature of more recently active dunes. 
Finally, in the Apollinaris Sulci, the MOC re-imaged dunes already known from the Viking orbiters that are so old -- and again, "fossilized" -- they bear the repeated trace of impact craters peppering their surface.
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