False colour image of a volcano on Io, as snapped by NASA’s Galileo spacecraft NASA/JPL
The largest and most powerful volcano on Jupiter’s moon Io erupts like clockwork and is set to go off again imminently. It also seems as if the interval between eruptions is getting shorter, but we don’t know why.
It is typically hard to predict when volcanoes will erupt because there are many different geological forces at play. But this volcano on Io, named Loki after the trickster Norse god, periodically brightens and dims, and those bright periods tip us off to impending explosions.
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“Sometimes for a couple hundred days it’ll be pretty dim, not much will be going on. And then for another couple hundred days in a row, it’ll be 15 to 20 times brighter, when its active,” says Julie Rathbun at the Planetary Science Institute in Arizona. She presented her latest observations of Loki on 17 September at a joint meeting of the European Planetary Science Congress and the Division for Planetary Sciences in Geneva, Switzerland.
Using NASA’s Infrared Telescope Facility in Hawaii, Rathbun tracks Loki’s brightness every week. She correctly predicted the last eruption in May 2018 and says Loki is set to blow again any day.
Rathbun’s observations previously showed that the volcano erupted about once every 540 days in the 1990s. But the intervals have shortened: now it’s about once every 475 days. She says we don’t know why it is happening more often.
“Usually you can’t really predict volcanoes well because there are so many forces at work. But my thought is that Loki is so large that any of the normal little geological perturbations, a fracture here or there, end up not complicating it,” she says.
Loki is huge. And when it is active, it accounts for about 15 per cent of the total heat flow on Io, even though the moon is covered in about 400 volcanoes. “There’s nothing comparable on Earth, not a thing. It would take out all of Southern California if it was on the Earth,” says Rathbun.
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