March 25, 2009--Dark splotches of dust create a unique pattern over branching troughs in a recently released image from the Mars Reconnaissance Orbiter.

Scientists think such troughs form as Mars's carbon dioxide ice caps sublimate, or turn directly from ice into vapor, in the spring. In some places gas flowing under the ice escapes, and the dust it carries from beneath the ice on the Martian surface falls back down to create the fan-shaped deposits.

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