... Last December, a dense sheet of gamma rays only a few times wider than the Earth plowed through our Solar System, saturating satellites and noticeably reflecting off the Moon. Oklo: Ancient African Nuclear Reactors . ... First imaged by the Mariner 9 spacecraft, Valles Marineris, the grand canyon of Mars, is a system of enormous depressions or chasmas that stretch some 4,000 kilometers along the Martian equator. ... Inside the nebula lies an open cluster of bright young stars designated NGC 2244. ...