Grand Canyon:1700m deep, 18km wide, 443km long. Ganges Chasma: 5000m deep, 160km wide, 800km long. Twice the length - Three times deeper - An order of magnitude wider - Ganges Chasma is more grand than the mighty Grand Canyon. And it is not even the largest canyon on Mars. It is, however, much more enigmatic. But nonetheless beautiful. It sports some interesting features, as well. Notice in the top center of the frame, where the canyon wall turns sharply from north to east, there is a large slide of debris off the canyon wall. This not unusual. It happens frequently on Mars. So what makes this different? Notice above the slide area, on the plateau, there is what appears to be an ejecta blanket. Could it be that the edge of the canyon was struck by a large meteor, causing the wall to collapse from the force of the collision? On the lower left side of the image, there is a large impact crater. While its full store is unknown, we can say that the crater was filled in somehow, its floor collapsed, and it filled to overflow by a liquid that was almost certainly water. The water carved a channel through the crater wall and across the plateau. Gange Chasma formed after the initial flow. This is apparent because there is a remnant of the channel farther down along the canyon. It appears that there may have been a smaller flow after the formation of Ganges. The source of the water and the collapse of the crater floor are definitely linked. The water erupted from the ground and in the process destabilized the crater floor. The material then collapsed into the ground, as occurs in a sinkhole. This is most likely how the formation of Ganges itself began. For what ever reason, the process continued in Ganges but was halted here. The northern part of the canyon is dominated by a large mound. This is likely the remnants of the plateau that was once continuous in this area. Alternatively it could be material that was deposited in the canyon after its formation. The mound has been substantially eroded. It displays intricate layering and wind blown, erosional features. The western end of the canyon floor is covered by dust. Some links Full Size JPeg ASU context Mars Global Surveyor / USGS context Vallis Marinaris - the Largest Valley System on Mars Visible Light Images of the Ganges Chasma: 
 
Grand Canyon: Video - Simulated Flyover Three D 
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