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Noctis Labyrinthus/Valles Marineris

October 8, 2009
The transition zone between maze-like troughs of Noctis Labyrinthus and the main Valles Marineris canyon system are shown in this THEMIS visible camera image. This huge system of troughs near the equator of Mars was most likely created by tectonic forces which pulled apart the crust. In the top third of the image, on the western side of the northernmost trough, a buildup of relatively bright material on the plateau has led to an overflow into the trough. Most of the bottom of this trough is covered by sediment deposited from the plateau above. On the right-hand side of this same trough, on the southern wall, there is a thin streak of darker material that also seems to originate from the plateau above. This is most likely a gully formation. This feature could also be a dust avalanche, but because no other similar features are seen, this is unlikely. Other dark material deposited by some unknown process can also be seen all around the easternmost ridge in the trough. Near the bottom of the canyon, layers from the center ridges and the canyon wall can be matched, indicating that the ridges are made of the same material as the wall. Near the bottom of the image, there is yet another depression. This trough is filled with sediment deposited from erosion of the trough wall and possibly from the plateau above. This sediment has been blown by the wind into sand dunes. All around the walls of this trough a layer of rocky material can be also be seen. It appears that the areas directly below the rocky ledges are "shielded" from landslide material from above. Finally, in the northwestern wall of this trough, there is an irregular pattern of very bright material not seen anywhere else in the image. Identifying similar formations in other THEMIS visible camera images could provide some context for its occurrence and help us understand how it was formed.


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