This photograph of the Moon's surface was taken by the American physicist Lewis Morris Rutherfurd in 1865. The two large craters with bright rays of impact debris extending out from them are called Tycho (upper right) and Copernicus (center right) after the Renaissance astronomers Tycho Brache and Nicholas Copernicus. The rays formed when debris was hurled hundreds of kilometers out from the impact site before falling to the ground because of the Moon's low gravity. Their brightness indicates that this occurred quite recently, as they have not yet been obscured by subsequent impacts.