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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This image is located in Utopia Planitia, a large plain in the northern hemisphere. It is believed that this basin is the result of a large impact. On the right side of the image is a partially imaged crater with a well-preserved ejecta blanket.

The morphology of the ejecta implies that the crater is young relative to the surrounding material and has not undergone extensive deposition or erosion. Surrounding the crater are polygonal troughs in the smooth surface material.

This polygon pattern is relatively common in the northern plains of Mars, and are primarily located in Acidalia Planitia, Elysium Plantia, and Utopia Planitia. These troughs are believed to be small grabbens, however, scientist are currently debating the origin of these features.

The two most accepted hypotheses are that these grabbens either form as volcanic material cools and contracts, or are produced as sediment shrinks as a result of compaction.