New secrets about Jupiter's volcanically volatile moon Io have been revealed by NASA's Juno probe.
Io, Jupiter's third-largest moon, is covered in lakes made of lava, according to a new paper in the journal Nature Communications Earth and Environment.
This discovery was made thanks to Juno's Jovian Infrared Auroral Mapper (JIRAM) instrument, designed by the Italian Space Agency, which detected the infrared light given off by the boiling-hot lava lakes.
Io, discovered in 1610 by Galileo Galilei, is considered the most volcanically active body in our solar system, with hundreds of volcanos scattered across its surface. These volcanoes have been seen to expel huge clouds of sulfur and sulfur dioxide. This volcanic activity is thought to be driven by tidal heating, with the gravitational push and pull exerted by Jupiter and the other moons generating friction and heat deep inside Io.
Lava lakes on Io's surface had previously been found in a few locations, such as the 127-mile-long lake Loki Patera. This study reveals that these lakes are extremely common on the moon, and the whole of its surface is dotted with them.
"The high spatial resolution of JIRAM's infrared images, combined with the favorable position of Juno during the flybys, revealed that the whole surface of Io is covered by lava lakes contained in caldera-like features," Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, said in a NASA statement. "In the region of Io's surface in which we have the most complete data, we estimate about 3 percent of it is covered by one of these molten lava lakes."
The lava lakes appear to be mostly covered in a thick molten skin, with a ring of exposed lava around their perimeters, data from Juno shows.
The data behind these discoveries were made in May and October 2023, when Juno did flybys of Io, coming within 22,000 miles and 8,000 miles of its surface. The JIRAM instrument spotted infrared signals that gave away the presence of the hot rings surrounding the lava lakes.
"We are just starting to wade into the JIRAM results from the close flybys of Io in December 2023 and February 2024," Scott Bolton, principal investigator for Juno at the Southwest Research Institute in San Antonio, said in the statement. "The observations show fascinating new information on Io's volcanic processes. Combining these new results with Juno's longer-term campaign to monitor and map the volcanoes on Io's never-before-seen north and south poles, JIRAM is turning out to be one of the most valuable tools to learn how this tortured world works."
These rings indicate something about the internal dynamics of the moon: Since the lava doesn't appear to extend past the edge of the lake, this implies that the melted rock is recycled regularly from the lake back below the ground.
"We now have an idea of what is the most frequent type of volcanism on Io: enormous lakes of lava where magma goes up and down," said Mura. "The lava crust is forced to break against the walls of the lake, forming the typical lava ring seen in Hawaiian lava lakes. The walls are likely hundreds of meters high, which explains why magma is generally not observed spilling out of the paterae (bowl-shaped features created by volcanism) and moving across the moon's surface."
The researchers suggest that these lava rings are created either by magma welling up into the lake and forming a crust that sinks at the edges and exposes the lava, or alternatively, due to the crust moving up and down as a surface and breaking at the edges.
"One possibility is that there might be upwelling in the middle of the patera. The insulating crust spreads radially via convection processes in the lake and then sinks at the edges, exposing lava. However, foundering of the lake crust at the walls does not necessarily produce spattering or exposure of molten lava," the researchers wrote in the paper. "Alternatively, a simple up-and-down "piston-type" movement of the entire lake surface may cause disruption of the lava lake crust against the patera walls to reveal hotter material."
Juno will collect further data about Io and Jupiter's other moons during its 63rd flyby of Jupiter on July 16.
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Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
