Io Volcanoes
Composite image Jupiter’s moon Io (credit: Galileo mission)
The volcanic moon Io presents geology at its most extreme.
When the Galileo spacecraft arrived at Jupiter in 1995, it wasn't known if volcanoes existed on the moon. During the first flyby of Io, active eruptions were photographed. The Galileo mission has ended but so much data and photography was gathered about the giant gas planet and its moons (Io, Europa, Ganymede, and Callisto) that analysis of the information is still in progress. During its flybys, Galileo discovered that Io has hundreds of active volcanoes, mountain ranges the float on continental size land masses, and a surface that is constantly being reformed by the lava geysers and lakes. When the New Horizons spacecraft flew by Jupiter 2007 it used the planet for a course correction to reach the outer planets and took more images of Io photographs as well.
Io eruptions video seen by New Horizons (credit: NASA/Johns Hopkins University)
Still reviewing the Galileo data, exciting new finding still are being made. During an international geology conference, a discovery was announced for a type of vulcanism, similar to Italy's Stromboli volcano, on Io. Using infrared data from Galileo's spectrometer, investigators were able to determine Io's heat radiance. The 'heat signatures' were similar to what has been seen during eruptions on Stromboli. The island off the coast of Sicily, is one of the most active volcanoes on Earth. Such temperature measurements will help determine the composition of Io's lava and rock types.
The surface of Io isn't the only geologic feature to constantly fluctuate. Land-based telescope and spectrographic data has revealed Io's sulfur dioxide (SO2) atmosphere completely collapses as snow at -270F when the moon is behind Jupiter with no warming by the Sun. The atmosphere reforms when the moon returns to the sunlight.
It would be exciting if a future mission to Jupiter might be able to orbit Io for closer measurements. However, chances of it surviving the extreme radiation conditions that close to Jupiter are low.
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