These colorful images are of thin slices of meteorites viewed through a polarizing microscope. Part of the group classified as HED meteorites for their mineral content (Howardite, Eucrite, Diogenite), they likely fell to Earth from 4 Vesta, the mainbelt asteroid currently being explored by NASA's Dawn spacecraft. Credit: NASA / JPL-Caltech / Hap McSween (Univ. Tennessee), A. Beck and T. McCoy (Smithsonian Inst.)