By: SPACE.com Staff
Published: 10/19/2012 07:25 AM EDT on SPACE.com
Saturn's icy medium-size moons were born when a few much bigger satellites collided to form the ringed planet's huge moon Titan, a new study suggests.
The Saturn system started out with a family of several relatively large moons like the Galilean satellites of Jupiter (Ganymede, Europa, Callisto and Io), according to the new theory. But things changed with a few dramatic moon mergers, which created the Titan we know today and shed enough material to form satellites such as Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus, researchers said.
"We think that the giant planets got their satellites kind of like the sun got its planets, growing like miniature solar systems and ending with a stage of final collisions," lead author Erik Asphaug, of the University of California, Santa Cruz, said in a statement.
"In our model for the Saturn system, we propose that Titan grew in a couple of giant impacts, each one combining the masses of the colliding bodies, while shedding a small family of middle-sized moons," Asphaug added. [Photos: The Rings and Moons of Saturn]
Earth's moon is thought to have formed from a giant impact about 4.5 billion years ago. And just as the moon and Earth are geochemical twins, the half-dozen or so medium-size moons of Saturn are similar in composition to Titan's icy mantle, researchers said.
"Our model explains the diversity of these ice-rich moons and the evidence for their very active geology and dynamics," Asphaug said. "It also explains a puzzling fact about Titan, in that a giant impact would give it a high orbital eccentricity."
Both Jupiter and Saturn have more than 60 known moons, but many of them are quite small, measuring just a few miles across. Scientists think most of these "moonlets" are captured asteroids or minor planets, or their remnants.
Asphaug and co-author Andreas Reufer, of the University of Bern in Switzerland, modeled the giant impact scenario using computer simulations.
They found that mergers between bodies the size of Jupiter's Galilean moons — which range from 1,940 miles (3,122 kilometers) wide in the case of Europa to 3,271 miles (5,264 km) across for Ganymede — would rip icy material from the outer layers of the colliding satellites.
This stuff would form ice-rich spiral arms, which would then clump together by gravitational attraction and create Saturn's medium-size moons (which are generally a few hundred miles across).
"These satellite collisions are a regime that is not very well understood, so the modeling opens up new possibilities in general for planet formation," Reufer said.
The moon mergers may have happened long ago. Or they could be more recent phenomena spurred by gravitational disruption caused by a migrating giant planet such as Uranus or Neptune, researchers said.
"What makes the Saturn system so beautiful and unique could be its youth," Asphaug said. "While we don't have a preferred timeframe for this origin scenario to play out, it could have happened recently if something came along to destabilize the Saturn system, triggering the collisional mergers that formed Titan."
New observations from NASA's Cassini spacecraft, which has been studying the Saturn system since 2004, should help the researchers know if their model is on the right track, Asphaug said.
"Our model makes strong predictions for how Titan was assembled, what the middle-sized moons are made of, and how they started out as rapidly spinning clumps of ice-rich material," he said. "So it's testable. These little moons could provide the clues telling us what happened, and when."
Asphaug and Reufer will present their model Friday (Oct. 19) at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nev. The new study will also be published in an upcoming issue of the journal Icarus.
Follow SPACE.com on Twitter @Spacedotcom. We're also on Facebook & Google+.
Copyright 2012 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Our 2024 Coverage Needs You
It's Another Trump-Biden Showdown — And We Need Your Help
The Future Of Democracy Is At Stake
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
The 2024 election is heating up, and women's rights, health care, voting rights, and the very future of democracy are all at stake. Donald Trump will face Joe Biden in the most consequential vote of our time. And HuffPost will be there, covering every twist and turn. America's future hangs in the balance. Would you consider contributing to support our journalism and keep it free for all during this critical season?
HuffPost believes news should be accessible to everyone, regardless of their ability to pay for it. We rely on readers like you to help fund our work. Any contribution you can make — even as little as $2 — goes directly toward supporting the impactful journalism that we will continue to produce this year. Thank you for being part of our story.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
It's official: Donald Trump will face Joe Biden this fall in the presidential election. As we face the most consequential presidential election of our time, HuffPost is committed to bringing you up-to-date, accurate news about the 2024 race. While other outlets have retreated behind paywalls, you can trust our news will stay free.
But we can't do it without your help. Reader funding is one of the key ways we support our newsroom. Would you consider making a donation to help fund our news during this critical time? Your contributions are vital to supporting a free press.
Contribute as little as $2 to keep our journalism free and accessible to all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you'll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.