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Discovery of Io’s Magma Chambers

Scientists from NASA’s Juno mission to Jupiter have discovered that the volcanoes on the planet’s moon Io are likely fueled by individual magma chambers rather than a single global magma ocean. This breakthrough resolves a 44-year-old mystery about the source of Io’s dramatic volcanic activity. P The discovery was published on December 12 in the journal *Nature* and highlighted during a media briefing at the American Geophysical Union’s annual meeting in Washington, the largest gathering of Earth and space scientists in the U.S. Unveiling the Mystery of Io’s Volcanoes About the size of Earth’s Moon, Io is known as the most volcanically active body in our solar system. The moon is home to an estimated 400 volcanoes, which blast lava and plumes in seemingly continuous eruptions that contribute to the coating on its surface. Although the moon was discovered by Galileo Galilei on Jan. 8, 1610, volcanic activity there wasn’t discovered until 1979, when imaging scientist Linda Morabito of NASA’s Jet Propulsion Laboratory in Southern California first identified a volcanic plume in an image from the agency’s Voyager 1 spacecraft. Juno’s Close Encounters with Io The Juno spacecraft made extremely close flybys of Io in December 2023 and February 2024, getting within about 930 miles (1,500 kilometers) of its pizza-faced surface. During the close approaches, Juno communicated with NASA’s Deep Space Network, acquiring high-precision, dual-frequency Doppler data, which was used to measure Io’s gravity by tracking how it affected the spacecraft’s acceleration. What the mission learned about the moon’s gravity from those flybys led to the new paper by revealing more details about the effects of a phenomenon called tidal flexing. Understanding Tidal Flexing Io is extremely close to mammoth Jupiter, and its elliptical orbit whips it around the gas giant once every 42.5 hours. As the distance varies, so does Jupiter’s gravitational pull, which leads to the moon being relentlessly squeezed. The result: an extreme case of tidal flexing — friction from tidal forces that generates internal heat. “This constant flexing creates immense energy, which literally melts portions of Io’s interior,” said Bolton. “If Io has a global magma ocean, we knew the signature of its tidal deformation would be much larger than a more rigid, mostly solid interior. Thus, depending on the results from Juno’s probing of Io’s gravity field, we would be able to tell if a global magma ocean was hiding beneath its surface.” Implications for Planetary Science “Juno’s discovery that tidal forces do not always create global magma oceans does more than prompt us to rethink what we know about Io’s interior,” said lead author Ryan Park, a Juno co-investigator and supervisor of the Solar System Dynamics Group at JPL. “It has implications for our understanding of other moons, such as Enceladus and Europa, and even exoplanets and super-Earths. Our new findings provide an opportunity to rethink what we know about planetary formation and evolution.”