This animation flickers between two Mars Orbiter Camera views of a gully in Naruko Crater in Terra Sirenum, Mars. The two images were captured in December 2001 and April 2005, and show that, between those two dates, liquid water flowed down the gully and left a light-toned deposit. The movement of other features in the image is due to the different points of view obtained by Mars Global Surveyor on the sloped crater wall in the two observations.

NASA / JPL / MSSS / Emily Lakdawalla