Given its similarities to its neighbor Saturn, it seems natural to wonder why Jupiter doesn’t also have a beautiful and vast ring system visible.
Alas, this is not the reality. Although Jupiter has rings, they are fine, tenuous and fragile dust, visible only when backlit by the Sun.
According to new research, these discount rings lack bling because Jupiter’s cluster of chonky Galilean moons keep discs of rock and dust from building up like they do around Saturn.
“It bothered me for a long time that Jupiter didn’t have even more amazing rings that would put Saturn to shame,” said astrophysicist Stephen Kane of the University of California, Riverside.
“If Jupiter had them, they would appear even brighter to us, because the planet is so much closer than Saturn.”
To interrogate the idea of a giant ring system forming around Jupiter at some point in its history, Kane and his colleague, UC Riverside astrophysicist Zhexing Li, conducted a series of simulations of the objects. orbiting the Jovian system.
These simulations took into account the orbital motion of Jupiter and the motions of its four largest moons, also known as the Galilean moons: Ganymede (which is larger than Mercury and the largest moon in the solar system), Callisto, Io and Europe. Into this mix, the team added the time it would take for a ring system to form.
According to this modeling, Jupiter cannot have Saturn-like rings — and it’s unlikely it ever did, the researchers said.
“Massive planets form massive moons, which prevents them from having substantial rings,” Kane explained. “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 ring that might form.”
Jupiter’s currently fragile rings are mostly made of dust ejected by some of its moons, possibly including material thrown into space from impact events.
Saturn’s rings, on the other hand, are mostly made of ice; perhaps fragments of comets or asteroids, or an icy moon that either broke apart due to Saturn’s gravity or collided in such a way that the ejecta formed rings.
We know that Saturn’s moons play an important role in forming and maintaining its rings. But a large enough moon (or moons) can also gravitationally perturb the rings, knocking ice out of planetary orbit into the big who knows where.
Although Saturn is the planet we all think of as the one with the rings, rings around planets are actually quite common, even here in the solar system.
There is Jupiter, of course, as we just said. The ice giants Neptune and Uranus also have thin and tenuous dust rings.
Uranus is also tilted sideways, relative to the other planets, with its orbital axis nearly parallel to the orbital plane. Her rings are believed to be related to this in some way; either something hit Uranus and knocked it sideways, or it once had absolutely huge rings, which could have caused it to tilt sideways.
And rings aren’t even limited to planets. A small body about 230 kilometers (143 miles) in diameter, called Chariklo, orbiting between Jupiter and Uranus, has rings. The same goes for the dwarf planet Haumea, which hangs out in the Kuiper Belt with Pluto. Simulations suggest that rings around icy bodies are not uncommon, due to gravitational interactions lifting ice from the surface of said bodies, to form an orbiting ring around them.
Mars also can sometimes have rings. Its moon Phobos gets a tiny bit closer to the red planet each year; in 100 million years, it will be close enough to be torn apart by Mars’ gravity, forming a short-lived ring that could eventually reform into a moon. Even Saturn’s rings are likely to be temporary, destined to slowly rain down on the planet.
If we can examine them in sufficient detail, the rings can be used to piece together some violent aspects of a planet’s history.
“For us astronomers, it’s the blood splatter on the walls of a crime scene,” Kane said. “When we look at the rings of the giant planets, that’s evidence that something catastrophic happened to put this material there.”
Anyway, it would be just as well if Big Jupe didn’t have spectacular rings. Let Saturn have its thing. Jupiter has already beefed up on the hexes, after all.
The research was accepted in the Journal of Planetary Scienceand is available on arXiv.