Japan Geoscience Union Meeting 2025

Presentation information

[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)

11:00 AM - 11:15 AM

[PPS01-08] Constraints on the Formation of Large Icy Moons from Gravity Field Measurements by Space Missions

*Yuhito Shibaike1,2 (1.Kagoshima University, 2.National Astronomical Observatory of Japan)

Keywords:Icy Moons, Pebble Accretion, Internal Structure, JUICE, Europa Clipper

Although many formation scenarios for the large icy moons around Jupiter and Saturn have been proposed, none of them has been universally accepted as the true history of their formation. One possible clue to solving this problem is revealing the internal structures of these moons.

For example, Callisto is estimated to have an only partially differentiated internal structure, based on measurements of its gravitational field by the Galileo mission. This suggests a slow accretion process for the moon's material. More detailed measurements of the gravity fields of the Galilean moons by the JUICE and Europa Clipper missions will further constrain their formation scenarios.

In particular, the pebble accretion scenario, which has been the subject of recent studies, could allow the moons to form without full differentiation. In this talk, I will compare the thermal conditions of the interiors of forming moons under two formation scenarios: the recent pebble accretion model and the classical satellitesimal accretion model. If future missions confirm that pebble accretion played a role in the formation of icy moons, this could provide the first evidence of pebble accretion—a process that has not yet been directly confirmed, even in the context of planet formation.