Orogeny on Io: how do you Make Mountains on Jupiter's Moon?

Mountains aren't the first thing that hit you when you look at images of Jupiter's innermost moon, Io. But once you absorb the fact that the moon is slathered in sulfurous lava erupted from 400 active volcanoes, you might turn your attention to scattered bumps and lumps that turn out, on closer inspection, to be Io's version of mountains.There are about 100 of them, and they don't look anything like the low lying volcanoes.

They also don't look like mountains on our home world. While we favor majestic ranges stretching from horizon to horizon, the mountains on Io are isolated peaks of great height that jut up out of nowhere. From space, they look rather like the blocky chips in the fancier kind of chocolate chip cookie.

For planetary geophysicists like William McKinnon, professor of earth and planetary science in Arts & Sciences at Washington University in St. Louis, the mountains of Io are an intriguing puzzle. By what process consistent with everything that is known about Io could these bizarre mountains have formed?

Since Io buries the evidence of its tectonic processes under a continually refreshed coating of lava (adding 5 inches a decade), the scientists have turned increasingly to computer simulations to solve the problem. In the May 16 online advance issue of Nature Geoscience, McKinnon and Michael T. Bland, a research space scientist at the USGS Astrogeology Science Center in Flagstaff, Ariz., publish a computer model that is able to make numerical mountains that look much like the jutting rock slabs on Io.

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