Astronomers at the Massachusetts Institute of Technology believe they may have cracked the age-old mystery of how Saturn’s trademark rings were formed.


What You Need To Know

  • Astronomers at the Massachusetts Institute of Technology believe they may have cracked the age-old mystery of how Saturn’s trademark rings were formed

  • In a study published Thursday in the journal Science, the researchers propose that the rings are remnants from when one of Saturn’s many moons disintegrated

  • The researchers believe the rings began to form around 160 million years ago when one of Saturn’s then 83 moons became unstable, veered too close to the planet and then was ripped apart by gravitation forces; a fraction of the wreckage ended up in the planet’s orbit and eventually flattened to form the rings

  • The missing moon theory also might explain Saturn’s tilt and its gravitational history with Neptune

In a study published Thursday in the journal Science, the researchers propose that the rings are remnants from when one of Saturn’s many moons disintegrated.

The missing moon theory also might explain Saturn’s tilt and its gravitational history with Neptune.

For many years, scientists believed Saturn’s rings formed more than 4 billion years ago when comets and asteroids were trapped in the planet’s orbit and eventually flattened into the rings we see now. But a number of space probes — Voyagers 1 and 2 in the 1980s and Cassini from 2004-17 — cast doubt on that explanation by revealing the rings were much younger than originally thought.

In their study, the MIT astronomers used computer simulations and data collected by Cassini, which orbited Saturn 294 times before it finally burned up, intentionally, while moving closer to the planet and obtaining vital information, including about Saturn’s gravitation pull.

The researchers believe the rings, mostly made up of ice ranging from the size of dust to houses, began to form around 160 million years ago when one of Saturn’s then 83 moons became unstable, veered too close to the planet and then was ripped apart by gravitation forces. About 99% of the moon’s wreckage crashed into Saturn’s atmosphere, but the rest remained in the planet’s orbit and eventually flattened to form the rings, according to the study, which was funded by NASA and the National Science Foundation.

The scientists named the missing moon Chrysalis, which they estimate was about the size of Saturn’s third largest moon, Iapetus. 

“Just like a butterfly’s chrysalis, this satellite was long dormant and suddenly became active, and the rings emerged,” said Jack Wisdom, professor of planetary sciences at MIT and the study’s lead author.

The Chrysalis theory also might explain why Saturn, which has 82 moons today, rotates at about a 27-degree angle relative to the plane in which it orbits the sun. 

Before Cassini data debunked the theory, scientists believed Saturn and Neptune were gravitationally interacting. The MIT study concluded the planets may have been in sync at one time but are no longer. The tilt, they found, resulted after Chrysalis’ demise, which released Saturn from Neptune’s grasp.

“It’s a pretty good story, but like any other result, it will have to be examined by others,” Wisdom said. “But it seems that this lost satellite was just a chrysalis, waiting to have its instability.”

In an editorial that accompanied the paper in Science, Dr. Maryame El Moutamid, a planetary dynamicist at Cornell University who was not involved in the study, wrote that the new research represents “a completely new scenario that may solve the age of the rings for good.”

Saturn’s rings extend up to 175,000 miles but are only about 30 feet thick. It’s not the only planet in the solar system with rings — Jupiter, Uranus and Neptune have them, too — but Saturn’s are the biggest and brightest.

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