Triton may have an active core today, new study finds
Internal magnetism could complicate hunt for a subsurface ocean on Neptune's largest moon
Voyager 2 imaged about 40% of Triton’s surface, shown here as a color mosaic. This image showed that Triton’s surface is surprisingly young, meaning that its icy shell keeps resurfacing. Unfortunately, Voyager 2 was too far away to determine if Triton generates its own magnetic field, like Ganymede does today. Credits: NASA/JPL-Caltech.
Triton is Neptune’s largest moon, and it might hide an ocean beneath its icy surface.
NASA’s Voyager 2 last visited Triton in 1989. Now, scientists consider it a top target for future missions. They want to learn more about its young surface, active plumes, and how it interacts with radiation from Neptune and the sun.
A recent study in Nature Astronomy suggests that Triton has an active magnetic field today, driven by vigorous churning of its metal core. The first author of the study is Lana Tilke, a PhD candidate in astrophysics at Arizona State University’s School of Earth and Space Exploration.
Tilke led a research team that made computer models of Triton’s evolution over billions of years. The team discovered that the metallic core is likely to start freezing, producing crystallized minerals that drive fluid motions in the core. Likewise, the gradual freezing of Earth’s inner core is a primary source of power for our global magnetic field.
If Triton has an active magnetic field, it could make searching for an underground ocean more difficult. For instance, NASA’s Europa Clipper mission will look for changes in Jupiter’s magnetic field caused by electric currents in Europa’s ocean. Scientists want to use similar methods at Triton, but a strong magnetic field from its core could be much stronger than any signals from a possible ocean.
“Planetary magnetism is one of the few ways that we can elucidate the conditions of a planetary body’s deep interior,” said Tilke. “I hope that we conduct further exploration of Triton soon, but even if such a mission is decades away, this work will help ensure its success.”
“When we search for an ocean of water at Triton, we might find the strongest signals from an ocean of metal, instead,” said Joseph O’Rourke, an associate professor in the School of Earth and Space Exploration who supervised the project. “Ultimately, we are offering a prediction, but the only way to reveal Triton’s secrets is to visit it again.”
To make this prediction about Triton, Tilke used models based on Ganymede, which is the only moon in the solar system with a known active magnetic field today. Ganymede is Jupiter’s largest moon and the biggest in the solar system. It is also the target of ESA’s Jupiter Icy Moons Explorer — or Juice — mission, which launched in 2023.