The revolutionary scientific work On the Origin of Species by Charles Darwin was published in 1859. Courtesy of Huntington Library hide caption

itoggle caption Courtesy of Huntington Library

A close-up composite image of a dust particle. The green patches contain bromine, calcium and/or iron. Courtesy of American Chemical Society hide caption

itoggle caption Courtesy of American Chemical Society

A team at NASA tests possible maneuvers for the Mars rover Spirit to use to escape the soft soil it has been stuck in since April. NASA/JPL-Caltech hide caption

itoggle caption NASA/JPL-Caltech