What chemical element makes the surface of Mars appear red?
Mineralogy of Mars is somewhere between the basalt or andesite rocks on Earth. This led to the formation of minerals similar to what is found on Earth. The presence of iron oxide gives the surface the “rust” color that is associated with Mars, the Red Planet. The presence of perchlorate, in high percentages, forms highly saline soils, which could produce liquid water. Chemical alteration of Martian rocks into carbonate and phyllosilicate minerals occurred earlier in Mars history when water was present in large quantities. Orbital instruments and Landers not only identified new minerals but in some cases also confirmed the presence of minerals
Mars surface color effect is that when quartz is fructured by the grinding, certain chemical bonds get broken at the newly exposed surfaces; when these surfaces come in contact with magnetite, oxygen atoms may be transferred from quartz surface to magnetite, forming hematite. Approximately true-colour "in situ" images from the Mars Pathfinder and Mars Exploration Rover missions indicate that the Martian sky may also appear reddish to humans. Absorption of sunlight in the 0.4-0.6 µm range by dust particles may be the primary reason for the redness of the sky. An additional contribution may come from the dominance of photon scattering by dust