Juno and Galileo’s volcanic activity on Io, Jupiter’s innermost Galilean moon and the most volcanically active object in the solar system, is unlikely to originate from a global magma ocean just below the surface. Deep space networks and astronomical observations, according to new analysis of Doppler data.
The internal structure of Io revealed by this research. Image credit: Sofia Shen / NASA / JPL / Caltech.
Slightly larger than Earth’s moon, Io is the most volcanically active object in the solar system.
It is the innermost of Jupiter’s Galilean moons, which in addition to Io includes Europa, Ganymede, and Callisto.
Trapped in a gravitational tug of war between Jupiter, Europa, and Ganymede, Io is constantly squeezed, causing frictional heat to build up within its interior, which is thought to be the cause of sustained and widespread volcanic activity.
Volcanic activity on the Moon was first discovered in 1979. That’s when Linda Morabito, an engineer on NASA’s Voyager program, spotted an eruption plume in one of the images taken by the spacecraft during its famous Grand Tour of the outer planets.
Since then, countless observations have been made from both space telescopes and telescopes on Earth documenting Io’s restless nature.
“Io is Galileo’s innermost moon, orbiting Jupiter every 42.5 hours,” said Juno collaborator Dr. Ryan Park of NASA’s Jet Propulsion Laboratory and colleagues.
“It has an average diameter of 3,643 km and a bulk density of 3,528 kg/m.3 As such, it is approximately 5% larger than the Moon, both in diameter and density.”
“Io’s eccentric orbit changes its distance from Jupiter by about 3,500 km, which leads to fluctuations in Jupiter’s gravitational pull.”
“Similar to the Moon’s tides caused by Earth, these gravitational fluctuations cause tidal deformations on Io, which are theorized to serve as the main energy source for the intense volcanism and infrared radiation observed on Io’s surface.”
The amount of tidal energy could be enough to cause Io’s interior to melt, potentially forming a magma ocean underground, but this theory is controversial.
Measuring the extent of Io’s tidal deformation could help determine whether the shallow magma ocean theory is plausible.
“Since the discovery of Morabito, planetary scientists have wondered how volcanoes were fed by lava beneath the Earth’s surface,” said Scott Bolton, Ph.D., principal investigator at Juno and a researcher at the Southwest Research Institute.
“Was there a shallow ocean of white-hot magma that fueled the volcano, or was the source more local?”
“We knew data from Juno’s two very close approaches could give us insight into how this beleaguered satellite actually works.”
Io’s arctic region was captured by NASA’s Juno on December 30, 2023, during the spacecraft’s 57th approach to the gas giant. Image credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt.
NASA’s Juno spacecraft flew very close to Io in December 2023 and February 2024, coming within about 1,500 km of the surface.
During its approach, Juno communicated with NASA’s Deep Space Network and acquired high-precision dual-frequency Doppler data. This data was used to measure Io’s gravity by tracking how it affects the spacecraft’s acceleration.
Combining these observations with archival Doppler data from NASA’s Galileo mission and ground-based telescopes, the researchers calculated how much Io is deformed by tidal forces.
This result is inconsistent with what would be expected if a shallow global magma ocean existed, suggesting that Io has a nearly solid mantle.
It is not yet known whether there are regions of magma deep within the moon.
The findings show that tidal forces do not necessarily create global magma oceans, which could have implications for our understanding of other moons such as Enceladus and Europa.
“Juno’s discovery that tidal forces don’t always produce global magma oceans not only prompts us to rethink what we know about Io’s interior,” Dr. Park said.
“It has implications for our understanding of other moons such as Enceladus and Europa, as well as exoplanets and super-Earths.”
“Our new findings provide an opportunity to rethink what we know about planet formation and evolution.”
The team’s paper published in this week’s magazine nature.
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RS Park others. Due to Io’s tidal reactions, shallow magma oceans do not form. nature published online on December 12, 2024. doi: 10.1038/s41586-024-08442-5
Source: www.sci.news
