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Eruption of the Tvashtar volcano on Jupiter’s moon Io, photographed by New Horizons, 1 March 2007, during its gravity-assist Jupiter flyby on its way to Pluto. I’ve brightened the pictures so that some detail on the darker part of Io is clearer.
The gif covers about 8 minutes of real time. If you count pixels and look up Io’s diameter, it looks like the plume’s “only” being thrown up to an altitude of 200km or so. But in fact the volcano is in the opposite hemisphere to the one we see here (albeit at a high latitude of about 67 degrees), and the plumes are reaching a height of over 300km.
There is much more detail about this volcano at the Gish Bar Times blog.
Earth, photographed by Galileo after its first gravity-assist flyby of the planet.