Astronomy

Via: Phil Plait
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Rabe formed in an instant when a large rock slammed into the surface of Mars long ago. It may have started as a normal, if large, impact crater, but things change. The cause of the flat floor isn't well known, but likely due to volcanic deposits filling it, plus material blown in over time.

Actually, that last bit is very important. Mars has an atmosphere, though a thin one, pushing down with less than 1% of the pressure on the surface as Earth's air does here. But it's enough.
A gorgeous nebula
Via: NASA
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Via NASA:
<blockquote>The W-shaped ridge of emission featured in this vivid skyscape is known as the Cygnus Wall. Part of a larger emission nebula with a distinctive outline popularly called The North America Nebula, the cosmic ridge spans about 20 light-years. Constructed using narrowband data to highlight the telltale reddish glow from ionized hydrogen atoms recombining with electrons, the two frame mosaic image follows an ionization front with fine details of dark, dusty forms in silhouette. Sculpted by energetic radiation from the region's young, hot, massive stars, the dark shapes inhabiting the view are clouds of cool gas and dust with stars likely forming within. The North America Nebula itself, NGC 7000, is about 1,500 light-years away.</blockquote>