Juno’s Jovian InfraRed Auroral Mapper (JIRAM) located the heat source on December 16, 2017, when the probe passed about 290,000 miles (470,000 km) from Io and captured an infrared image of its southern hemisphere.
The innermost of Jupiter’s four Galilean moons and fourth largest, with a diameter of 2,264 miles (3,640 km), Io is the most volcanically active world in the solar system. Jupiter’s powerful gravitational pull as well as the gravitational influence of the other three Galilean moons, Ganymede, Europa, and Callisto, power Io’s churning interior.
“The new Io hot spot JIRAM picked up is about 200 miles (300 km) from the nearest previously mapped hot spot,” said Juno co-investigator Alessandro Mura of the National Institute for Astrophysics (INAF) in Rome. “We are not ruling out movement or modification of a previously discovered hot spot, but it is difficult to imagine one could travel such a distance and still be considered the same feature.”
Approximately 150 active volcanoes have been previously discovered on Io by numerous spacecraft, including Voyagers 1 and 2, Galileo, Cassini, and New Horizons. Some spew lava as high as 250 miles (400 km) into space.
Scientists believe as many as 250 additional volcanoes have yet to be discovered on Io.
Future flybys will come even closer to the giant planet and its moons. Data collected during those flybys will be analyzed in conjunction with that collected last December.
Since entering Jupiter orbit on July 4, 2016, Juno has traveled in an elliptical orbit around the giant planet, conducting close flybys every 53 days to study the planet’s cloud tops and look beneath them at its auroras to learn more about Jupiter’s formation, evolution, composition, magnetic fields, gravitational fields, and structure.
During these close flybys, Juno flies as low as 2,100 miles (3,400 km) above Jupiter’s cloud tops.
Currently, the $1.1 billion mission, which has flown almost 146 million miles (235 million km) since entering orbit around Jupiter, is set to end in July 2021.
The probe will begin its 13th close flyby of Jupiter starting on July 16.