NASA's Dawn Probe Ends Primary Mission, May Visit 3rd Cosmic Object

NASA's Dawn spacecraft has completed its historic primary mission, during which the probe became the first ever to visit a dwarf planet and the first to orbit two different bodies beyond the Earth-moon system. Dawn is still studying the dwarf planet Ceres from orbit, and the probe may soon head out to visit a third cosmic object, if NASA approves a proposed extended mission. Dawn orbited the 330-mile-wide (530 kilometers) Vesta from July 2011 through September 2012, and the probe has been circli