Jupiter’s volcanic moon Io appears to have no underground magma ocean, which resolves some questions about how Io’s volcanoes erupt and raises broader questions about similar magma oceans within other moons and planets.
Data from previous missions has planetary scientists wondering whether Io contains not just some molten rock but a 31-mile (50-kilometer-deep) magma layer: a moon-wide ocean of molten rock. In the 1990s, magnetic induction measurements by NASA’s Galileo mission revealed the existence of such a layer, and more recently, the distribution of volcanoes on Io mapped by NASA Juno mission Jupiter It is thought to imply that a global magma ocean radiates heat on the moon.
But Juno’s new measurements, plus the space center’s archival data Galileo Missionseems to have ruled out a possibility Magma ocean beneath the surface of Io.
As many as 400 volcanoes are erupting on the surface of Jupiter’s innermost moon Ionearly every square inch of the moon is covered in lava plains. Erupting lava (lava that reaches the surface) comes from “melted” areas within the Earth’s mantle, which are areas of rising magma (lava that is still underground).
The energy to melt the rocks in Io’s mantle would come from tidal heating controlled by Jupiter’s gravitational field. Io orbits Jupiter in an eccentric orbit that may be 2,175 miles (3,500 kilometers) away from the giant planet. This means that the gravitational pull it feels from Jupiter changes throughout its orbit, twisting and squeezing the moon’s interior, causing energy to be released in the form of heat.
plus similar but smaller gravitational tides from other satellites Europa, Ganymede and Callistowhich means that a large amount of tidal energy can be injected into the interior of Io, but is this enough to completely melt a layer of the mantle?
Juno arrived at Jupiter in 2016 and has orbited the giant planet more than 60 times, but over the past few years it has been getting closer to Jupiter and flying past Galileo’s large moon. December 30, 2023 and February 3, 2024, Juno flies within 930 miles (1,500 kilometers) of Io.
It has since conducted more flybys of Io, and close to Io, the moon’s gravity interfered with radio signals sent from Juno to the spacecraft. Combining archival data from the Galileo spacecraft, researchers led by Ryan Park of NASA’s Jet Propulsion Laboratory were able to exploit Io’s gravitational field during the two flybys, as well as when the volcanic moon was squeezed by Jupiter. and how the gravitational field changes when stretched.
If Io does have an underground magma ocean, the moon would be significantly deformed by Jupiter’s gravity. However, Doppler measurements show that Io is quite rigid, meaning its interior is quite solid. There can be no magma ocean.
If there is no magma sea, where does the “melt” in the form of lava in volcanoes come from? On Earth, melting is produced by tectonic forces. Because the melt is less dense and therefore more buoyant than the surrounding solid mantle, the magma rises and erupts through the volcano. Although there does not appear to be a global magma ocean on Io, there must be some magma that rises through volcanoes and flows out to the surface.
A comparison can be made between Io and Io Earthof moonalso. At first glance, they don’t look much alike—Earth’s moon is barren and inert, Io is covered in volcanoes. However, Io’s diameter and density are only 5% larger than the moon. Additionally, for the first 100 million years of our moon’s existence, it did have a magma ocean, due to its violent childbirth Debris from a massive impact on the young Earth. Gradually, heat leaked from Earth’s moons and the magma ocean solidified. Parker’s team believes that tidal heating alone is not enough to form a magma ocean—it would take a dramatic event like the formation of the moon to generate enough energy.
The findings also have wider implications exoplanet. Astronomers have discovered many exoplanets orbiting the smallest stars, called M dwarf. Being so close, they would be subject to tidal heating, and astronomers wonder whether they might have a global magma ocean. The Io-Jupiter system is similar in scale to exoplanets orbiting M dwarfs, and if Io’s volcanoes do not have magma oceans, then exoplanets in close orbits around M dwarfs may not have either.
The findings were published in the journal Nature.