Jupiter’s moon Io, which is as full of volcanoes as a porcupine is full of quills, is the most volcanically active world in the solar system. At any given time, about 150 of Io’s 400 or so active volcanoes are erupting. The moon is constantly spewing lava and gas, a veritable factory of volcanic excretions.
And thanks to the Juno probe’s Jovian Infrared Auroral Mapper (JIRAM), which is imaging Jupiter and its surroundings, we now know a lot more about the deliciously hot mess on Io.
“The high spatial resolution of JIRAM’s infrared images, combined with Juno’s favorable position during the flybys, revealed that Io’s entire surface is covered with lava lakes in caldera-like structures,” said astrophysicist Alessandro Mura of the National Institute of Astrophysics in Italy.
“In the region of Io’s surface for which we have the most complete data, we estimate that about 3 percent of it is covered by one of these molten lava lakes.”
Io is the victim of a complicated game of gravitational tug. Its orbit around Jupiter is not perfectly circular, meaning that the gravitational pull between the moon and the planet changes in intensity over time. In addition, Jupiter’s other Galilean moons—Callisto, Europa, and Ganymede—have enough mass to exert their own gravitational pull on Io.
The result of all these conflicting gravitational influences is stress on Io’s interior, generating heat that gushes out in the form of volcanism. The small moon is a hot potato.
While we have a fairly good understanding of the dynamics that are squeezing and stretching Io’s innards, and the effects of this on the broader environment of Jupiter and the giant gas planet itself, there is still much we do not know about how the volcanism manifests itself on Io’s surface.
Fortunately, that fell under Juno’s purview. As the probe explores Jupiter’s space, it’s conducting flybys of several of its moons, using its instruments to gather data closer and more personal than we’ve ever gotten before. The probe recently performed a series of very close flybys of Io, revealing the sulfurous moon in astonishing detail.
We’ve seen plumes from real volcanic eruptions, and lakes of lava glistening on the surface. Now scientists have analyzed some of that data, specifically infrared observations captured by JIRAM, which reveal heat signatures on Io’s surface.
This allowed scientists to observe lava lakes consisting of a ring of exposed liquid lava sloshing at the edges, with a hardening crust in the center of the molten lake, forming the high lake walls around the bowl-shaped patera in which the lava collects. This ultimately reveals the most dominant form of volcanism on Io.
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“We now have an idea of the most common type of volcanism on Io: huge lava lakes where magma flows up and down,” Mura says.
“The lava crust is forced to break against the lake walls, creating the typical lava ring seen in Hawaiian lava lakes. The walls are probably hundreds of meters high, which explains why magma generally does not flow out of the paterae and over the walls. the moon surface.”
This suggests that lava enters the patera from a magma reservoir beneath the surface and flows out in the same manner, causing the lakes to rise and fall. The central crust rubs against the sides of the lake as it rises and falls, causing the edges to break off and a ring of lava to form around the perimeter of the lake.
Another possibility is that the edges of the Earth’s crust become heavier and sink beneath the lava, creating a ring again.
“The observations provide fascinating new information about the volcanic processes on Io,” said Scott Bolton, principal investigator for Juno and a member of the Southwest Research Institute in the US.
“Combining these new results with Juno’s long-term campaign to monitor and map the volcanoes at Io’s never-before-seen north and south poles, JIRAM proves to be one of the most valuable tools for learning how this troubled world works.”
The research was published in Nature communication.