Jupiter's Volcanic Moon Io Continues to Surprise Scientists

Scientists have published five years of observations of Jupiter’s volcanic moon Io, revealing just how strange the world is. They even describe one volcano that might be influenced by the moon’s orbit. 

Io is the solar system’s fourth-largest moon and most volcanically active object. The five years of infrared observations go against scientists’ models of the planet—all of the brightest eruptions seem to occur on only one of Io’s hemispheres, for example. Io’s extreme volcanic activity makes it a prime observation target for astronomers.

“If we want to understand volcanic activity more generally, rather than from an Earth-centric perspective, then Io is the place to go study in terms of how geologically active it is,” Katherine de Kleer, assistant professor in planetary science at CalTech, told Gizmodo. 

Io’s volcanoes have long presented a mystery. They seem to be scattered in a less-than-random way across the surface, with fewer at the poles or on the parts of the moon that face away from Jupiter (like our own moon, one side of Io always faces Jupiter). Researchers observed Io for a combined total of 271 nights between 2013 and 2018, using the Keck and Gemini North telescopes, both on Mauna Kea in Hawai’i. During this run, the researchers captured several new eruptions and new hotspots, as well as 113 flashes from Io’s most powerful volcano, Loki Patera.

The team’s initial analysis, published recently in The Astrophysical Journal, has already revealed that the planet’s eruptions are generally hot, just under 1,000 degrees Fahrenheit. And all of the brightest eruptions happened on the hemisphere that faces away from the direction Io moves around Jupiter, though the total amount of energy released during the eruptions was the same on both the leading and trailing sides of the moon. This result wasn’t well-explained by theoretical predictions of Io, de Kleer said.

De Kleer also led a second analysis of Loki Patera’s behavior from 1987 to 2018. These results, published in Geophysical Research Letters, seem to demonstrate that variations in the volcano’s activity correlate with changes to Io’s orbit; the moon orbits Jupiter every 1.77 days, but the orientation changes every 480 days. This offers some evidence that the volcano’s behavior is tied to the gravitational pull of Jupiter. But de Kleer told Gizmodo that these results are still preliminary, and that some predictions can hopefully be tested with more data in order to prove the hypothesis. 

It’s innately interesting to learn about the workings of a distant moon, but there are also some things Io can tell us about Earth, de Kleer said. The volcanism is higher temperature than Earth with more magma, but looks similar to the volcanic activity thought to be present on Earth during its early history. Io gives a look into the processes that shape planets and moons, and how they’re changed by their environments.

Researchers hope to take more observations of Io and add in data from complimentary missions, such as Juno. Maybe, reports Nat Geo, researchers will one day get a spacecraft to visit the moon directly.