Astronomers have uncovered new evidence that Jupiter’s moon Callisto likely harbors a massive underground ocean, potentially joining Europa and Ganymede as another water-rich world in the outer solar system. By reanalyzing data from NASA’s Galileo mission, a team of researchers successfully filtered out decades-old interference caused by Callisto’s intense ionosphere, revealing a signal that strongly suggests the presence of a global saltwater ocean beneath the icy crust.
This discovery could have significant implications for future missions searching for habitable environments beyond Earth, with upcoming spacecraft like NASA’s Europa Clipper and the European Space Agency’s JUICE mission set to provide further confirmation in the next decade.
New Analysis Confirms a Hidden Ocean Beneath Callisto
For decades, scientists have theorized that Callisto, Jupiter’s second-largest moon, could contain an underground ocean, but past magnetometer readings were too clouded by interference to provide definitive proof. Now, a new study published in Earth and Space Science presents a breakthrough method for detecting subsurface oceans, and its application to Callisto has provided strong evidence that the moon harbors a vast body of liquid water beneath its icy crust.
The study, led by Corey J. Cochrane and his team, introduces a Principal Component Analysis (PCA)-based approach to analyzing magnetic induction data—a method that allows scientists to differentiate between a genuine ocean signature and interference caused by Callisto’s ionosphere and background noise. By applying this technique, researchers were able to isolate a clear and distinct magnetic response, strongly suggesting that a salty ocean lies beneath the moon’s surface.
This discovery not only adds Callisto to the growing list of potentially habitable icy worlds in our solar system but also demonstrates how advances in data processing techniques can unlock new insights from decades-old mission data. With future missions like NASA’s Europa Clipper and ESA’s JUICE set to study the Jovian system in greater detail, scientists now have a powerful new tool to confirm and explore the depth, salinity, and habitability of Callisto’s hidden ocean.
Could Callisto’s Ocean Support Life?
Callisto is often overshadowed by its more famous neighbor Europa, which has long been considered one of the most promising locations for extraterrestrial life due to its subsurface ocean and geological activity. However, Callisto’s lower radiation levels and abundant surface oxygen make it a potentially intriguing target for astrobiology as well.
While scientists remain cautious about whether life could exist in Callisto’s ocean, its chemical composition and interaction with Jupiter’s magnetic field could reveal new insights into the conditions necessary for habitability.
“Europa Clipper is actually a habitability mission (not to be confused with life detection), which will provide the data required to better help us answer this question,” Cochrane noted.
Future Missions Will Provide the Final Answer
NASA’s Europa Clipper, launching in 2024 and set to reach Jupiter by 2030, will be equipped with advanced magnetometers and radar instruments capable of probing Callisto’s interior with far greater precision. Meanwhile, ESA’s JUICE (Jupiter Icy Moons Explorer), expected to arrive in 2031, will also perform detailed studies of Callisto, Europa, and Ganymede.
Cochrane emphasized that more data is the key to confirming the ocean’s depth and thickness, stating, “For every flyby that occurs, only a very small snapshot in time of the magnetic field environment is captured. The new missions will help ‘fill in the holes’ left by Galileo’s limited data.”
If confirmed, Callisto would become the third Jovian moon with a known subsurface ocean, adding to the growing list of potentially habitable environments in our solar system.
