Just outside of Eos Chasma in eastern Valles Marineris is a unit of light-toned material on the plains. Plains on Mars are typically dark-toned and formed by the lava from volcanic eruptions.

One possibility for the light-toned nature of the plains in this image is a deposit other than lava. Compositional information from other instruments orbiting Mars, such as the CRISM spectrometer (also on the Mars Reconnaissance Orbiter) could shed insight into what is causing the light-toned nature of this unit.

Many dark circular features in the light-toned deposit are impact craters that have been filled in with darker material, such as basalt sand. The dark-toned unit that surrounds the light-toned one has linear ripples not seen on the light-toned unit. If the dark-toned unit represents an aeolian deposit, then the light-toned unit in the image may be clean rock exposures not yet covered by this aeolian (wind created) material. In this second possibility, the reason the unit appears light-toned is simply because it is adjacent to an even darker unit, but compared to other lava plains on Mars, the light-toned unit may not be unusual.



Written by: Cathy  (18 July 2007)