Why doesn’t Jupiter have rings?

Since it is bigger, Jupiter should have larger, more spectacular rings than Saturn. For a long time, scientists have puzzled why this is not the case. Now, a research team led by the University of California, Riverside (UCR) has found that Jupiter’s massive moons have a crucial role in preventing the formation of rings around the planet.

“It’s long bothered me why Jupiter doesn’t have even more amazing rings that would put Saturn’s to shame,” said study lead author Stephen Kane, an astrophysicist at UCR. “If Jupiter did have them, they’d appear even brighter to us, because the planet is so much closer than Saturn.” Another thing that puzzled Kane was whether Jupiter once had such amazing rings and somehow lost them.

To clarify why Jupiter currently looks the way it does, Dr. Kane and his graduate student Zhexing Li ran a dynamic computer simulation that accounted for the orbits of Jupiter’s four moons, the orbit of the planet itself, while integrating information about the amount of time it takes for rings to form.

Saturn’s famous rings are largely made of ice, part of which may have come from comets. However, if a planet’s moons are large enough – as is Jupiter’s case – their gravity can toss the ice out of a planet’s orbit, or change the ice’s orbit 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 explained. “Massive planets form massive moons, which prevents them from having substantial rings.” These findings suggest that it is unlikely that Jupiter had large rings in the past.

However, all four giant planets from our solar system – Saturn, Uranus, Neptune, and even Jupiter – do in fact have rings. Nevertheless, Neptune and Jupiter’s rings are so flimsy that they were impossible to observe with traditional astronomical instruments. Recently though, images from the newly commissioned James Webb Space Telescope included pictures of Jupiter, in which the faint rings are indeed visible. “We didn’t know these ephemeral rings existed until the Voyager spacecraft went past because we couldn’t see them,” Dr. Kane said.

Besides their breathtaking beauty, rings help scientists learn more about the history of a planet, since they offer evidence of collisions the planet had with other celestial bodies. The shape, size, and composition of the rings can offer valuable indications about the types of events that formed them.

“For us astronomers, they are the blood spatter on the walls of a crime scene. When we look at the rings of giant planets, it’s evidence something catastrophic happened to put that material there,” Dr. Kane concluded.  

The study is published in the journal Planetary Science.

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By Andrei Ionescu, Earth.com Staff Writer