Scientists have obtained their closest view yet of Saturn's tiny moon Epimetheus. Taken by the Cassini spacecraft, the portrait shows that the moon, whose name in Greek means "afterthought", has an irregular shape and is pocked with soft-edged craters. The high density of these craters implies that the surface of Epimetheus is several billion years old.
Once every 4 years, the 16-kilometer-wide body exchanges orbits with Janus, a slightly bigger Saturnian moon. The gravitational gyrations of these shifts create waves within Saturn's icy rings. Spectra of Epimetheus taken by Cassini's visual and infrared mapping spectrometer indicate that the moon is mostly water ice.