Image from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showing a series of troughs and layered mesas in the Gorgonum Chaos region of the Martian southern hemisphere. Gullies proposed to have been formed by seeping ground water emanate from a specific layer near the tops of trough walls, particularly on south-facing slopes (south is toward the bottom of each picture). The presence of so many gullies associated with the same layer in each mesa suggests that this layer is particularly effective in storing and conducting water. Such a layer is called an aquifer, and this one appears to be present less than a few hundred meters beneath the surface in this region.
The MOC picture was taken on January 22, 2000. Sunlight illuminates the scene from the upper left. The image is located near 37.5°S, 170.5°W. The height of this image section spans about one km. MOC 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.
Image courtesy NASA/JPL/Malin Space Science Systems.
Image contrast and brightness increased by author.