Scientists are releasing a picture each weekday from the Mars Odyssey spacecraft. Odyssey's Thermal Emission Imaging System (THEMIS) captures the images as the craft orbits Mars. The photos are not yet fully calibrated for scientific use, and so no formal science findings are being discussed, said researchers who operate the camera from Arizona State University.

Today's picture ...

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Cerberus is a dark region on Mars that has shrunk down from a continuous length of about 622 miles (1000 km) to roughly three discontinuous spots a few 65 miles (100 kms) in length in less than 20 years. There are two competing processes at work in the Cerberus region that produce the bright and dark features seen in this THEMIS image.

Bright dust settles out of the atmosphere, especially after global dust storms, depositing a layer just thick enough to brighten the dark surfaces. Deposition occurs preferentially in the low wind "shadow zones" within craters and downwind of crater rims, producing the bright streaks.

The direction of the streaks clearly indicates that the dominant winds come from the northeast. Dust deposition would completely blot out the dark areas if it were not for the action of wind-blown sand grains scouring the surface and lifting the dust back into the atmosphere. Again, the shadow zones are protected from the blowing sand, preserving the bright layer of dust. Also visible in this image are lava flow features extending from the flanks of the huge Elysium volcanoes to the northwest.

Two shallow channels and a raised flow lobe are just barely discernable. The lava channel in the middle of the image crosses the boundary of the bright and dark surfaces without any obvious change in its morphology. This demonstrates that the bright dust layer is very thin in this location, perhaps as little as a few millimeters.