A fresh volcano with lava flows spanning hundreds of kilometres has appeared on Jupiter鈥檚 moon Io. It has formed in the 27 years between flybys of two spacecraft.
Astronomers first took detailed photos of Io, the most volcanically active body in the solar system, with NASA鈥檚 Galileo spacecraft, which was studying Jupiter and its moons between 1995 and 2003.
NASA鈥檚 Juno spacecraft, which has been orbiting Jupiter since 2016, has been taking increasingly close photos of Io over 2023 and 2024, documenting the stark changes all over the moon鈥檚 surface since Galileo鈥檚 flybys. Juno has also been examining the north and south of the moon more closely, which Galileo couldn鈥檛 see in much detail when it took photos in 1997.
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One of the most significant changes is the appearance of a new volcano near a region of active lava flows, called Kanehekili Fluctus, in the moon鈥檚 south-west.
The volcano, spotted by at space company Malin Space Science Systems and his colleagues, was visible in a nightside picture taken on 3 February, illuminated only by sunlight reflected from Jupiter. 鈥淲e observed surface changes in many, many different locations, on timescales of years and even months,鈥� Ravine told the in Berlin on 9 September.
There appear to be two active streams of lava coming from the volcano, each running for about 100 kilometres, on its west and south-western sides, as well as a large deposit of red sulphur, covering an area of about 60 by 90 kilometres, just to its east. The findings provide further evidence of just how volcanically active Io is.
Ravine and his team also spotted several new mountains on Io, some of which appear to be 7 kilometres tall with nearly vertical slopes. 鈥淭hey look like a bad map painting from a 1950s science fiction movie,鈥� said Ravine.
Not everyone at the conference was convinced that such steep, tall structures are real, when they could also be a misinterpretation of the pictures. 鈥淚t seems excessively unrealistic in terms of big, pointy [mountains],鈥� said at the University of Colorado, Boulder.
Ravine agreed that they are unusual, but said it is what his team鈥檚 calculations suggest, and that the mountains were unlikely to last for significant periods of time.
Some changes to Io鈥檚 surface also occurred between different Juno flybys, separated by just a few months. A striking 1000-kilometre-wide red ring surrounding a volcanic crater in the south-west of the moon, called , appeared in the two months between Juno鈥檚 3 February and 9 April flybys. This is likely to be caused by sulphur deposits from a volcanic plume, similar to other plumes and rings that have been seen on Io, said Ravine.
