From NASA's Planetary Photojournal
Gullies eroded into the wall of a meteor impact crater in Noachis Terra. This high resolution view from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) shows channels and associated aprons of debris that are interpreted to have formed by groundwater seepage, surface runoff, and debris flow. The lack of small craters superimposed on the channels and apron deposits indicates that these features are geologically young. It is possible that these gullies indicate that liquid water is present within the martian subsurface today.
The MOC image was acquired on September 28, 1999. The scene covers an area approximately 3 kilometers (1.9 miles) wide by 6.7 km (4.1 mi) high (note, the aspect ratio is 1.5 to 1.0). Sunlight illuminates this area from the upper left. The image is located near 54.8 degrees S, 342.5 degrees W. The MOC image is on the south-facing wall of an impact crater approximately 20 kilometers (12 miles) in diameter. The Mars Orbiter Camera high resolution images are taken black-and-white (grayscale); the color seen here has been synthesized from the colors of Mars observed by the MOC wide angle cameras and by the Viking Orbiters in the late 1970s. This is only a crude approximation of martian color and should only be considered representative of Mars. It is likely Mars would not look like this to a human observer at Mars.
Image Title: Evidence for Recent Liquid Water on Mars: Gullies in Crater Wall, Noachis Terra
Catalog #: PIA02988
Photo Credit: NASA/JPL/Malin Space Science Systems Target Name: Mars
Spacecraft: Mars Global Surveyor
Last Modified On: Monday, December 18, 2000