9 December 2010

Hell on Earth (and Io)

Posted by Ryan Anderson

If you don’t follow the Boston Globe’s photoblog The Big Picture, you’re really missing out. The topics range widely from current events to pictures of Saturn, and the photos are of course always stunning. Yesterday was an especially awesome set of photos from the indonesian sulfur mine Kawah Ijen. The photos were taken at night, and sulfur has the interesting quality that it burns blue, resulting in some spectacular and otherworldly scenes of fire and brimstone.

Most people don’t realize it, but pure sulfur has a pretty low melting point. In the photos of Kawak Ijen, you can see the molten sulfur flowing, but even sulfur mines here on earth pale in comparison to what’s happening on Jupiter’s moon Io. Io is about the size of the earth’s moon, but its orange and yellow and black surface betrays a very different history. The spectacular colors of Io’s surface are from different sulfur compounds that have been belched out of its thousands of volcanoes.

Unlike the earth’s moon which has been allowed to cool peacefully, Io is constantly stretched and distorted by Jupiter’s powerful tides. This keeps the interior nice and hot and powers constant volcanic eruptions. All of the more volatile compounds like carbon dioxide and water vapor were lost to space in eruptions long ago, but sulfur is just heavy enough to stay trapped by Io’s gravity. The result is that the surface is coated in colorful layers of sulfur from all the eruptions. Alas, there’s no oxygen for it to burn blue on Io, but some of the sulfur does manage to escape and get caught in Jupiter’s magnetic field. In fact, there is a stream of plasma pouring from Io onto Jupiter’s pole, making a lovely spot in the planet’s aurorae.

The northern lights on Jupiter. The tadpole-shaped blob on the left is caused by the stream of ions from Io.