Japan Geoscience Union Meeting 2025

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[E] Oral

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS01] Outer Solar System Exploration Today, and Tomorrow

Fri. May 30, 2025 10:45 AM - 12:15 PM 301B (International Conference Hall, Makuhari Messe)

convener:Jun Kimura(The University of Osaka), Kunio M. Sayanagi(NASA Langley Research Center ), Fuminori Tsuchiya(Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University), Shuya Tan(Japan Agency for Marine-Earth Science and Technology), Chairperson:Yoshifumi Saito(Solar System Science Division, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Shotaro Sakai(Department of Geophysics, Graduate School of Science, Tohoku University)

10:45 AM - 11:00 AM

[PPS01-07] A Critical Core Size for Dynamo Action at the Galilean Satellites

★Invited Papers

*Kevin T Trinh1, Carver J. Bierson1,2, Joseph G. O'Rourke1 (1.Arizona State University, 2.Scottsdale Community College)

Keywords:Europa, Ganymede, Callisto, Io, Dynamo, Core

Ganymede is the only known moon with an active dynamo. No mission has discovered intrinsic magnetism at the other Galilean satellites: Io, Europa, and Callisto. A dynamo requires a large magnetic Reynolds number, which in turn demands, for these moons, a large metallic core that is cooling fast enough for convection. Here we quantify these requirements to construct a regime diagram for the Galilean satellites. We compute the internal heat fluxes that would sustain a dynamo over the wide ranges of plausible radii for their metallic cores. Below a critical radius, no plausible heat flux will sustain a dynamo. Europa likely sits on the opposite side of this limit than Ganymede and Io. We predict that future missions may confirm a small (or absent) core, meaning that Europa could not sustain a dynamo even if its interior were cooling as quickly as Ganymede's core.