http://www.msss.com/mars_images/moc/2004/08/10/index.html

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired in March 2004, shows gullies formed in the wall of a south middle-latitude crater wall near 39.7°S, 208.6°W. The banked, curved nature of the channels in each gully are among the key indicators that a fluid, such as liquid water, may have been required to form them.