Solar system formation

At SciNews: Study: Massive Galilean Moons Prevented Formation of Giant Ring System around Jupiter

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Planetary rings are often speculated as being a relatively common attribute of giant planets, partly based on their prevalence within the Solar System. However, their formation and sustainability remain a topic of open discussion, and Jupiter — the most massive planet within our planetary system — harbors a very modest ring system.

A distinctive common feature of solar system giant planets is the presence of ring systems orbiting the planet.

Rings systems have been detected and studied extensively for each of Jupiter, Saturn, Uranus, and Neptune.

Jupiter and its Galilean moons: Europa, Ganymede, Io and Callisto. Image credit: Galileo Project / Voyager Project / NASA’s Jet Propulsion Laboratory.

In particular, the prominent rings of Saturn have been the source of numerous studies with regards to their formation and dynamics.

By comparison, Jupiter contains a substantially more modest ring system that has been extensively studied via data from such missions as Voyager and Galileo, as well as ground-based observations.

Theories regarding the origin and evolution of the Jovian rings vary, such as their possible formation along with the Galilean moons (Europa, Ganymede, Io and Callisto), and the contributions of collisional material lost from inclined satellites and escaping material from the Galilean satellites and/or the inner small moons.

Further possible sources of potential ring material originate from impact debris and the tidal disruption of satellites or large passing Kuiper Belt objects.

“It’s long bothered me why Jupiter doesn’t have even more amazing rings that would put Saturn’s to shame,” said lead author Dr. Stephen Kane, an astrophysicist in the Department of Earth and Planetary Sciences at the University of California, Riverside.

“If Jupiter did have them, they’d appear even brighter to us, because the planet is so much closer than Saturn.”

“I also had questions about whether Jupiter once had fantastic rings and lost them. It is possible for ring structures to be temporary.”

To understand the reason Jupiter currently looks the way it does, Dr. Kane and his colleague, University of California, Riverside graduate student Zhexing Li, ran a dynamic computer simulation accounting for the orbits of the Galilean moons, as well as the orbit of the planet itself, and information about the time it takes for rings to form.

Saturn’s rings are largely made of ice, some of which may have come from comets, which are also largely made of ice.

If moons are massive enough, their gravity can toss the ice out of a planet’s orbit, or change the orbit of the ice enough so that it collides with the moons.

“We found that the Galilean moons of Jupiter, one of which is the largest moon in our Solar System, would very quickly destroy any large rings that might form,” Dr. Kane said.

“As a result, it is unlikely that Jupiter had large rings at any point in its past.”

“Massive planets form massive moons, which prevents them from having substantial rings.”

The findings appear in the Planetary Science Journal.


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