The arrows in this picture, released July 15, 2004, from NASA's Mars Global Surveyor point to three boulders that left trails behind them as they rolled down the lower parts of a meteor crater's wall.

15 July 2004
The arrows in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture point to three boulders that left trails behind them as they rolled down the lower parts of a meteor crater's wall. In two cases, the tracks can be resolved into a series of small depressions, indicating the variable shape of the boulder as it unevenly proceeded down the slope. These features are located near 18.4°N, 120.1°W. The 75 meter scale bar is about 246 feet long. Sunlight illuminates the scene from the lower left.

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