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New Insights into Io’s Volcanism: A Solid Mantle Uncovered

A recent exploration into the geological makeup of Io, one of Jupiter’s fiercely volcanic moons, suggests the presence of a largely solid mantle beneath its surface. This revelation marks a significant shift in our understanding of the moon’s internal structure and volcanic activity.

NASA’s Juno spacecraft captured detailed images of the north polar region of Io during its 57th close approach to Jupiter on December 30, 2023. The spacecraft’s flybys are yielding crucial data that sheds light on the interior composition of this fascinating moon.

In contrast to previous theories proposing a subsurface global magma ocean beneath Io’s surface, a study published in Nature indicates that this isn’t the driving force behind the moon’s persistent volcanic activity. The research suggests that tidal flexing—caused by gravitational interactions with Jupiter—is central to generating the internal heat that fuels Io’s eruptions.

Understanding the Subsurface

Positioned in close proximity to Jupiter, Io experiences intense tidal forces that not only induce volcanic eruptions but were also believed to sustain a shallow reservoir of magma below the surface. However, according to Ryan Park, the lead author of the study and a senior research scientist at NASA’s Jet Propulsion Laboratory, the moon likely possesses a porous mantle. This porous structure may consist of molten rock existing in a slushy state, facilitating the movement of magma without requiring a large ocean.

Park compares this geological condition to that found under locations like Hawaii or Iceland, where solid rock is interspersed with melted material. “The rocks are partly molten, similar to under Hawaii or Iceland on Earth,” he explained. “It’s kind of like a slushy — solid material (ice) with melt (water) in the cracks in between. The melt eventually escapes to the surface and erupts.”

The study’s conclusions were drawn from Doppler data collected during two recent Juno flybys, along with earlier data from NASA’s Galileo spacecraft. As Juno passed by Io, its gravitational instruments measured the spacecraft’s acceleration changes, enabling researchers to assess the moon’s internal structure based on its gravitational interactions.

Implications for Other Celestial Bodies

The findings regarding Io’s solid mantle have broader implications for other celestial bodies in our Solar System. Europa, another of Jupiter’s moons, is strongly believed to harbor a water ocean beneath its icy veneer. The upcoming Europa Clipper mission, set to arrive at Europa in 2030, aims to investigate whether a significant ocean exists there. Park notes that the techniques used in studying Io could also be applied to Europa to assess its tidal deformation, potentially confirming or refuting the presence of a global ocean.

Additionally, these insights challenge existing theories about the asteroid Vesta, where earlier measurements suggested the possibility of past volcanic activity tied to a shallow magma ocean. The current findings introduce uncertainty regarding the nature of Vesta’s geology.

As Juno embarks on its 66th flyby of Jupiter, it continues to contribute to our understanding of Io from a distance. Although no close flybys are planned, Juno’s observations will provide further data on Io’s surface processes through visible and infrared measurements.

As scientists continue to unravel the complexities of Io’s geology, the implications of this research extend beyond the moon itself, offering valuable insights into the dynamic systems of other bodies within our Solar System.

Source
www.astronomy.com