Tvashtar

The image here shows the Tvashtar volcano erupting on Io, a moon of Jupiter. The image was actually acquired by the Pluto-bound spacecraft New Horizons. New Horizons used a Jupiter flyby a few months ago to gain speed for the long cruise out to Pluto. During the flyby New Horizons took advantage to study the moons of Jupiter as well as Jupiter itself. The Tvashtar plume, at the top of the image, reaches hundreds of miles into space. The plume is symmetric because Io has no real atmosphere so the erupted material follows perfect arc trajectories on all sides.