A Modern Dynamo as a Consequence of Triton’s Capture at Neptune

Abstract Triton, Neptune’s largest moon, is one of the highest-priority candidate ocean worlds to explore. Its capture and orbital circularization may have caused intense heating that led to internal differentiation and the formation of a metallic core. In this work, we argue that this “hot start” may lead to Triton hosting an active dynamo today, driven by ongoing convection within its metallic core. Using thermal evolution models, we explore three potential regimes of core crystallization to assess their impact on the likelihood of dynamo action. Our results imply that Triton, like Ganymede, may possess an ongoing dynamo that generates a magnetic field with field strengths on the order of ~1 μT at the surface. If confirmed, the existence of a dynamo would provide a unique constraint on Triton’s internal structure, composition, capture history, and evolution. Strong dynamo fields, however, would also complicate efforts to characterize the subsurface ocean via magnetometry.