James Townley, via Facebook asked:
What is the largest active volcano in the solar system?
We posed this question to Chris Kilburn from University College London...
Chris K - Well, to be honest, I suppose because "active" means we have to have seen this erupting, we have evidence that it was likely to, I’d guess we still have to stick with the Earth, and so that would be Hawaii. But volcanoes such as Olympus Mons on Mars for example are considered to be the largest volcanic edifices in the solar system. And some of the Jovian satellites, there is evidence of volcanic activity, but I'm afraid I don't know how big those volcanoes are. But certainly, I think we’ll stick for Hawaii now. Of course the Martians may have some interesting activity, should we ever finally set foot on Mars, you never know!