Surface units on Mars: The assemblage in the Valles Marineris

The Valles Marineris system of troughs offers a unique opportunity to investigate Martian surface units in the third dimension. The troughs are more than 7 km deep in places and thus expose a significant portion of the Martian upper crust. The geological units within the Valles Marineris can be subdivided into three broad categories: wall rock, interior deposits, and surficial cover. Overall, the exposure units in the Valles Marineris give insights into surface units elsewhere on Mars. The observations tend to support the hypotheses that the highland material is charaged with ice, that some light-colored, rolling, smooth deposits are of volcanic origin, and that dark dunes and streaks are composed of wind blown mafic materials.