Volcanoes on Io in unexpected arrangement

Los Angeles Times : Io is the innermost of Jupiter’s moons and is known for its exceptionally active volcanoes. The moon’s vulcanism is caused by the intense gravitational stresses on it from Jupiter and the planet’s other moons. Christopher Hamilton of NASA’s Goddard Space Flight Center in Maryland examined maps of Io’s volcanoes that have been constructed from pictures taken by the Voyager and Galileo spacecraft. He found that the clusters of volcanoes on Io’s surface were 30 to 60 degrees eastward of where they would be expected to be based on known gravitational stresses. The location indicates that the internal dynamics of the moon may differ significantly from what planetary scientists expect. Hamilton has performed similar research based on the patterns of volcanoes on Earth and Mars. He suggests that the variance from the prediction could be explained by a faster-than-expected rotation or that there is a vast layer of magma under the surface, similar to what is believed to have been present on our own moon .