Based on data gathered from ground-based telescopes, the Voyager and Galileo probes, and a number of other sources, scientists had thought to have created a comprehensive map of Io’s volcanoes. The map was, in part, derived from how volcanoes form here on Earth. Spots of the most intense geothermal heat were presumed to be the most likely spots for volcanoes to form.
With this map in hand, astronomers looked for confirmation of their theory. What Hamilton and his team found, however, was that Io’s volcanoes were substantially further east than they had presumed — about 30 to 60 longitudinal degrees to be precise.
There are a lot of factors in effect on Io that Earth need not undergo, and it may be due to one or more of these that Io’s volcanic eruptions are so far out of what we consider to be the norm. For instance, Io orbits Jupiter much more rapidly than either Ganymede or Europa, but the proximity of these other moons exerts a pull on little Io at regular intervals. This pull has stretched Io’s orbit into more of an oval than a circle, meaning that sometimes the moon is much closer to the giant gravitational pull of Jupiter than it would be otherwise.
NASA still isn’t sure whether it is the pull of Jupiter, Ganymede or Europa that is causing the discrepancy in their data. It isn’t even sure that it’s one of the three of these celestial bodies that’s at fault. What it does know is that there’s more to learn. An exciting prospect for any scientist.
( via dvice.com )