MGS MOC Release No. MOC2-535, 5 November 2003

This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle image of gullies carved into debris on the south-facing wall of Nirgal Vallis, an ancient martian valley. The gullies were conduits for sediment that has accumulated at a point where each channel met the valley floor. The aprons of debris are superposed upon the large ripple-like dunes, suggesting that the gullies are younger than these bedforms. Gullies such as these might have been formed by a liquid, such as water, seeping from the layered bedrock exposed in the valley wall, or perhaps by mass movement of the smooth-surfaced debris that covers much of the lower two-thirds of the valley wall. This picture is located near 28.6°S, 41.5°W. The image covers an area 3 km (1.9 mi) across and is illuminated by sunlight from the upper left.