The mystery of jupiter and saturn’s moons may have been solved

Artist”s impression of the simulations conducted in this research. Jupiter (lower left) has a strong magnetic field which creates a cavity in its circumplanetary disk. Saturn (upper right) lacks a strong magnetic field so its circumplanetary disk evolves without a cavity. Credit: Credit: Yuri I. Fujii/L-INSIGHT [Kyoto University], Illustrator: Shinichiro Kinoshita

doi.org/10.1038/s41550-026-02820-x
Credibility: 989
#Moons

Jupiter and Saturn are the two largest planets in our Solar System and, at first glance, seem very similar: both are gas giants. However, their moon systems are quite different, and this has intrigued scientists for a long time.

A new study suggests that the explanation lies in each planet’s magnetic field.

Jupiter has more than 100 moons, with four large and important ones: Io, Europa, Ganymede (the largest moon in the Solar System), and Callisto.

Saturn, in turn, has more than 280 moons and is famous for its rings, but stands out mainly for Titan, the second largest moon in the system.

Why does one planet have several large moons and the other basically only one large one?

Researchers from Japan and China, led by scientists from Kyoto University, have created a unified model to explain this difference using the same physical principles.

They simulated what planets were like at the beginning of their formation, analyzing temperature, magnetic field strength, and the disks of material that rotated around them (called circumplanetary disks), from which moons are born.

The results show that Jupiter’s strong magnetic field created a “cavity” within this disk of gas and dust.

This cavity acted as a kind of trap, protecting and maintaining large moons (such as Io, Europa, and Ganymede) as they formed and migrated.

Saturn, on the other hand, had a weaker magnetic field at the beginning, which did not allow the formation of this cavity.

Without this protection, most moons that attempted to form or migrate ended up being lost or destroyed.

This discovery helps us understand not only our Solar System, but also other distant planetary systems.

According to the model, large planets like Jupiter tend to form compact systems with several large moons, while planets the size of Saturn usually end up with only one or two main moons.

The study, published in the journal “Nature Astronomy,” opens a new avenue for studying moon formation throughout the Universe and shows how something seemingly invisible-the magnetic field-can completely shape the architecture of a planetary system.

Published in 04/16/2026 10h38

Portuguese version

Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.

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