These maps show a nontronite and hectorite are found commonly in the lower elevations of Mawrth Vallis while montmorillanite and other hydrated silicates are at higher elevations surrounding nontronite and hectorite.
12.
The dioctahedral sheet of nontronite is composed mainly of trivalent iron ( Fe 3 + ) cations, although some substitution by trivalent aluminium ( Al 3 + ) and divalent magnesium ( Mg 2 + ) does occur.
13.
Microorganisms are also involved in reduction of structural iron in nontronite when soils undergo anoxia, and the reduced form of the clay appears to be highly reactive towards certain pollutants, perhaps contributing to the destruction of these compounds in the environment.
