It takes a lot to get my jaw to drop - usually - but this sort of thing... wow. I get tingles up my spine still.
Here are some pics - first is an artistic picture chosen specifically because it would look neat:
Next are 2 shots of Io - this is an incredibly active moon at Jupiter, and in one of the shots a plume is visible near the top. The smaller picture is of Io in eclipse behind Jupiter's shadow. The luminescence is from the hot lava flows on the surface, active eruptions, and (surrounding the entire planet) the auroral glow caused by the extremely intense magnetosphere from Jupiter pummeling the moon with radiation.
From the New Horizons site:
The edge of Io's disk is outlined by the auroral glow produced as intense radiation from Jupiter's magnetosphere bombards the atmosphere. The glow is patchy because the atmosphere itself is patchy, being denser over active volcanoes. At the 1 o'clock position the giant glowing plume from the Tvashtar volcano rises 330 kilometers (200 miles) above the edge of the disk, and several smaller plumes are also visible as diffuse glows scattered across the disk. Bright glows at the edge of Io on the left and right sides of the disk mark regions where electrical currents connect Io to Jupiter's magnetosphere.