NASA’s Juno spacecraft has revealed that Jupiter’s moon Io is covered in lava lakes. The probe used its Jovian Infrared Auroral Mapper (JIRAM) instrument to detect the infrared light given off by these boiling-hot lakes. Io, discovered by Galileo Galilei in 1610, is the most volcanically active body in our solar system.

Its surface has hundreds of volcanoes that expel huge clouds of sulfur and sulfur dioxide. This activity is driven by tidal heating caused by Jupiter’s and its other moons’ gravitational pull. Previous studies have found lava lakes in a few locations on Io.

However, this new study shows that these lakes are widespread and dot the moon’s entire surface. The whole surface of Io is covered by lava lakes contained in caldera-like features,” said Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome.

Widespread lava lakes on Io

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.

The lava lakes appear to be mostly covered in a thick molten crust, with a ring of exposed lava around their edges. This data was collected during Juno’s flybys in May and October 2023, when it came within 22,000 miles and 8,000 miles of Io’s surface, respectively.

“We are just starting to wade into the JIRAM results from the close flybys of Io in December 2023 and February 2024,” said Scott Bolton, principal investigator for Juno at the Southwest Research Institute in San Antonio. The observations show fascinating new information on Io’s volcanic processes.”

The researchers suggest two possible ways these lava rings are created. One is that magma wells up into the middle of the lake, forming a crust that sinks at the edges and exposes the lava.

The other is that the crust moves up and down, breaking at the edges. Juno will collect more data about Io and Jupiter’s other moons during its next flyby of Jupiter on July 16, 2024. This will help scientists better understand the volcanic processes on this fascinating moon.