... M42: Wisps of the Orion Nebula . ... Here, glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1500 light-years away. ... Comet NEAT Passes an Erupting Sun . ... Just as the comet swooped inside the orbit of Mercury and developed a long and flowing tail of gas and dust, the Sun emitted a huge Coronal Mass Ejection (CME). ... But Mars is too cold and its atmosphere too thin for liquid water to exist on the surface. ... The planet Mercury resembles a moon....