... Although the scene may appear somehow supernatural, nothing more unusual is occurring than a setting Sun and some well placed clouds. ... Comet NEAT Passes an Erupting Sun . ... But Mars is too cold and its atmosphere too thin for liquid water to exist on the surface. ... First imaged by the Mariner 9 spacecraft, Valles Marineris, the grand canyon of Mars, is a system of enormous depressions called chasmata that stretch some 4,000 kilometers along the Martian equator. ... First page ] Prev. ...