24 October 2004
The northwest flanks of the broad, northern Tharsis volcano, Alba Patera, have been known since the 1970s to exhibit a plethora of what appeared to be branching valley networks running down the volcano slopes. Some investigators suggested that these valleys were evidence for precipitation and runoff of liquid water on the volcano flanks. It was hoped that high resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) would provide new details that would confirm or refute the hypothesis. The problem is, MGS MOC images instead showed a surface largely covered by an eroded, rough-textured mantle that obscured the valley floors. The images, such as the one shown here, also showed that the valleys are discontinuous and indistinct when viewed at high resolution (although, when shrunk to fit within the reduced-scale view on this web page, they may seem continuous -- click on the image to view the full-scale picture). The valleys in the lower quarter of this image have been cut by a fault. This image is located on Alba Patera near 45.8°N, 111.8°W. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.