Re:BepiColombo’s First Views of Mercury
by adrian_b on Monday October 04, 2021 @08:11AM
(#28745655)
The most abundant minerals in rocks in the solar system are white oxides, except for the iron(II) and manganese oxides, which are blackish.
So most rocks are gray, unless they have been exposed to oxygen, which converts the black iron oxide into red iron oxide, in which case the rocks turn from some gray shade to some brown shade.
Where there has been water, the water could have been dissociated by light, providing oxygen for the change of color. In the absence of water, there are few chances for anything else that could change the color of the rocks from gray.
So most rocks are gray, unless they have been exposed to oxygen, which converts the black iron oxide into red iron oxide, in which case the rocks turn from some gray shade to some brown shade.
Where there has been water, the water could have been dissociated by light, providing oxygen for the change of color. In the absence of water, there are few chances for anything else that could change the color of the rocks from gray.