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Volcano's on Io

Week of May 5, 1997

Quick: name four geologically active bodies in our Solar System!

picture of volcanic plume on Io

Well, there's the Earth, of course. Recently it's been found that Venus may have some active regions. Triton, Neptune's largest moon, has ice volcanoes. But probably the most interesting volcanoes are on Jupiter's moon Io.

Io is about the same size as our own Moon, but could not be more different. Io was discovered in the 1980's by the Voyager probes to have volcanoes which spew sulfur out in plumes hundreds of kilometers high. Some of the particles from these plumes actually manage to escape from Io, and they orbit Jupiter on their own. This ring of sulfur particles can be detected from the Earth!

The ring is constantly replenished by volcanic eruptions on Io. One of these was captured by the amazing Galileo probe currently performing its dance of gravity around Jupiter and its moons. The picture above shows Io, its left side lit by the Sun. The red spot just below center is Io's largest volcano, named Pele. But the tremendously bright spot on the right of Io is not a bright star: it's the plume of the volcano Prometheus catching the sunlight! The volcano itself is actually on the far side of the moon from this viewpoint, but the plume rose high enough to be seen by Galileo. And yes, those are actually stars in the background. In my opinion, this image is one of the most dramatic ever taken by a space probe.

Wanna know more?

Go to The Nine Planets to get general info about Io, Triton and any other solar system body.

Check out NASA's Galileo Probe Page for lots of great info about Galileo and pictures sent back from this scrappy fellow.

©2008 Phil Plait. All Rights Reserved.

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