Io Tvashtar Volcano There She Blows

This five-frame sequence of New Horizons images captures the giant plume from Io's Tvashtar volcano. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/SRI. Jupiter's moon Io is the most volcanically active world in the solar system, with hundreds of volcanoes, some erupting lava fountains up to 250 miles high (about 400 kilometers). However, concentrations of volcanic activity are significantly displaced from where they are expected to be, based on models that predict how the moon's interior is heated, according to NASA and European Space Agency researchers. The team, which includes ROSALY LOPES of NASA's JET PROPULSION LABORATORY, Pasadena, Calif., primarily used data from NASA's Voyager and Galileo missions. The new paper also analyzes data from other spacecraft and ground-based telescopes, but much of what scientists know about Io's surface comes from these two missions. Voyager, still being managed by JPL, discovered Io's volcanoes in 1979, making that moon the only body in the solar system other than Earth known to have active magma volcanoes. Galileo, which was also a JPL mission, flew by Io in 1999 and 2000. Io is caught in a tug-of-war between Jupiter's massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit farther from Jupiter -- Europa and Ganymede. Io orbits faster than these other moons, completing two orbits every time Europa finishes one, and four orbits for each one Ganymede makes. This regular timing means that Io feels the strongest gravitational pull from its neighboring moons in the same orbital location, which distorts Io's orbit into an oval shape. This, in turn, causes Io to flex as it moves around Jupiter. More from NASA JPL.