Saturn’s rings were once a moon torn apart by strange forces

Saturn’s rings Not only are they the most recognizable traits on the planet, but they are also among its most enigmatic. Scientists aren’t quite sure how the rings formed in the first place. The rings are likely relatively new features, forming in the past 100 million years or so. But despite being recent additions to the cosmic time scale, it’s always a mystery how they got there. Now, a new study suggests that the story of their creation may be rooted in destruction.

what’s new – in New study Published Thursday in the magazine SciencesResearchers suggest that the destruction of a former moon of Saturn, nicknamed Chrysalis, may help explain the mysterious origins of the planet’s rings. Moon havoc could also help solve a number of other scientific unknowns about the planet.

For example, Saturn’s tilt – the angle at which its axis of rotation is tilted relative to its orbit around the Sun – is much larger than expected. When gas giant worlds like Saturn formed from the protoplanet’s disk of gas and dust around the fledgling sun, researchers expect the resulting planets to orbit mostly with the direction in which they orbit the star. But Saturn’s tilt is about 26.7 degrees, which is much larger than the predicted 2 to 5 degrees, according to the study’s lead author jack wisdoma planetary dynamic scientist at the Massachusetts Institute of Technology inverse.

Wisdom and his team’s research suggests that Saturn’s former moon, Chrysalis, may answer both puzzles. They hypothesized that about 100 to 200 million years ago, Chrysalis met a horrific end, getting too close to its host planet and being torn apart in the process. The scattered debris became the planet’s small rings. Meanwhile, losing the Moon will also change the gravitational force acting on Saturn, change the planet’s moment of inertia, or how mass is distributed within the planet.

“It’s exciting to find a scenario that explains a number of things that were not previously thought to be related,” Wisdom says.

Daphnis, a small moon of Saturn, sculpts its circular shape. Since the rings were likely made from an ancient moon, this means that Daphnis is some type of said moon child. or something. NASA / JPL-Caltech / Space Science Institute

Digging into the details – Astronomers have long suspected that Saturn’s strange eccentricity is caused by gravitational interactions between Saturn and its fellow outer solar system planet. Neptune. The motion of Saturn’s tilt—that is, shifts over time, is much like how the top of the rotation tilts back and forth before it falls—at roughly the same rate as Neptune’s orbit.

This association is due to a phenomenon known as orbital resonance. When a pair of bodies orbit a common center – say, Saturn and Neptune, around the Sun – if the rate at which they orbit around this middle body, or some other aspect of their orbits, can be expressed as the ratio of a pair of integers, they are in orbital resonance . For example, two planets, both orbiting a parent star, are said to exist 2:1 chime When one of these worlds takes about twice as long as the other planet to orbit the star.

When two objects are in orbital resonance with each other, they exert a regular periodic gravitational effect on their partners. Imagine pushing the baby in a hammock – each repeated push will have a cumulative effect over time as the baby rises. In the case of Saturn and Neptune, the way certain aspects of their orbits align may cause these planets to have a certain orbital effect on their companions.

But notes from NASA Cassini The spacecraft, which orbited Saturn from 2004 to 2017, added a new wrinkle to the problem. Scientists found that Titan, the largest of Saturn’s 83 known moons, was moving away from the planet at a faster than expected rate, about 11 centimeters per year.

The researchers speculated that Titan’s rapid migration and gravitational pull interacted with Saturn in a way that helped Neptune tilt Saturn. But this explanation relied on a key unknown – Saturn’s moment of inertia, which is how mass is distributed in the planet’s interior.

Saturn as seen by the Cassini probe in 2009. NASA/JPL/Space Science Institute

How did they do it? Wisdom and his team combined gravity data from Cassini with a model of Saturn’s interior to infer the planet’s moment of inertia. Surprisingly, their findings suggest that although Saturn may have been in sync with Neptune, it is no longer so.

To find out how Saturn may have escaped its association with Neptune, researchers developed computer simulations to develop the motions of Saturn and its moons back in time to see if any natural orbital instability affected Saturn’s tilt. They didn’t find anything.

Scientists then examined what would happen if Saturn lost a moon. They ran computer simulations to estimate the properties of this moon, such as its mass and the distance it orbits around Saturn.

The researchers suggest that the gravitational pull of a hypothetical satellite, Chrysalis, may have helped keep Saturn’s tilt in sync with Neptune. Their model estimates that the cocoon was the size of Iapetus, Saturn’s third largest moon.

Wisdom and colleagues hypothesize that sometime between 100 million and 200 million years ago, Chrysalis entered a chaotic tropical region. She experienced a number of close encounters with Titan and Iapetus and “eventually had a pastoral encounter with Saturn, shattering it and forming rings,” says Wisdom.

Then, the loss of Chrysalis would have left Saturn escaping the grip of Neptune. The researchers say the cocoon’s unstable orbit may also help explain why Titan’s orbit is more elliptical than circular.

why does it matter – Understanding how Saturn’s iconic rings form has been a problem for astronomers for decades. After all, to understand how other planetary systems form, figuring out the processes that govern our solar system is key. In theorizing a lost moon may be the culprit, Wisdom offers a new interpretation of the rings and other weirdness of the gas giant in an elegant package.

“Previous simulations of ring formation from a disrupted comet body, similar to the mass we assume for Chrysalis, indicate that they provide sufficient mass to produce the current rings,” the researchers wrote in their paper.

“I’ve known about the age problem of the 100-million-year-old rings since I was a graduate student 40 years ago. So it’s exciting to come up with an explanation. We also naturally explain why Titan’s orbit is much further apart than expected.”