NASA has announced that the Juno spacecraft will make its closest pass yet on July 30 to one of Jupiter’s largest moons, Io. It is expected to come within 22,000 km of Io.
The NASA/JPL website reports that “data collected by the Italian-built JIRAM (Jovian InfraRed Auroral Mapper) and other science instruments is expected to provide a wealth of information on the hundreds of erupting volcanoes pouring out molten lava and sulfurous gasses all over the volcano-festooned moon.”
How can there be volcanoes on such a faraway moon, you ask? Io is caught in a perpetual tug-of-war between Jupiter, another moon Europa, and the biggest moon in the Solar System, Ganymede. The constant stretching and squeezing of the moon generates enormous friction and heat.
NASA explains: “These forces cause Io’s surface to bulge up and down (or in and out) by as much as 330 feet (100 meters). Compare these tides on Io’s solid surface to the tides on Earth’s oceans. On Earth, in the place where tides are highest, the difference between low and high tides is only 60 feet (18 meters), and this is for water, not solid ground.”
