As studded with volcanoes as a porcupine with scratches, Jupiter’s moon Io is the most volcanically active world in the Solar System. At any given time, about 150 of the approximately 400 active volcanoes on Io are erupting. It constantly spews lava and gas; a veritable factory of volcanic excrement.
And, thanks to the Juno probe’s Jovian Infrared Auroral Mapper (JIRAM) image of Jupiter and the surrounding environment, we now know a lot more about what an extremely hot mess Io is.
“The high spatial resolution of JIRAM’s infrared images, combined with Juno’s favorable position during the flybys, revealed that the entire surface of Io is covered by lava lakes embedded in caldera-like features,” says astrophysicist Alessandro Mura of the National Institute for. Astrophysics in Italy.
“In the region of Io’s surface where 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 complex game of gravitational pull. Its orbit around Jupiter is not perfectly circular, meaning that the attraction 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 a gravitational influence on Io.
The result of all this conflicting gravitational influence is stress on Io’s interior, generating heat that pours out in the form of volcanism. The small moon is a hot potato.
While we have a pretty good understanding of the dynamics that are squeezing and stretching Io’s interior, and the effect this all has on the wider environment around Jupiter and the gas giant itself, there is much we don’t know about how volcanism manifests on the surface of Io.
This, fortunately, fell under Juno’s responsibility. As the probe explores Jovian space, it is conducting flybys of some of the moons, using its instruments to gather data closer and more personal than we’ve ever been able to before. Recently, the probe conducted a series of very close flybys of Io, revealing the sulfurous moon in amazing detail.
We have seen the plumes of current volcanic eruptions and lava lakes glistening on the surface. Now, scientists have analyzed some of that data, in particular infrared observations captured by JIRAM, which reveal heat signatures on Io’s surface.
From this, scientists were able to observe lava lakes consisting of an exposed liquid lava ring that wraps around the edges, with a solidified crust in the center of the molten lake and forming high lake walls around the crater-shaped the bowl in which the lava collects. This finally reveals the most dominant form of volcanism on Io.
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“We now have an idea of what the most common type of volcanism is on Io: large lava lakes where magma flows up and down,” says Mura.
“The lava crust is forced to break against the walls of the lake, forming the typical ring of lava seen in Hawaiian lava lakes. The walls are likely to be hundreds of feet high, which explains why magma is generally not seen pouring out of the crater and move beyond on Monday surface.”
This suggests that lava enters the patera from a magma reservoir below the surface and drains in the same way, causing the lakes to rise and fall. The central crust rubs against the sides of the lake as it moves up and down, breaking the edges and resulting in a ring of lava around the perimeter of the lake.
The other possibility is that the edges of the crust thicken and sink under the lava, once again resulting in a ring.
“The observations reveal fascinating new information about Io’s volcanic processes,” says Juno principal investigator Scott Bolton of the Southwest Research Institute in the US.
“Combining these new results with Juno’s long-term campaign to monitor and map volcanoes at Io’s previously unseen north and south poles, JIRAM is proving to be one of the most valuable tools for learning how this works tortured world.”
The research was published in Nature Communications.