New simulations shed light on origins of Saturn’s rings and icy moons

- With images and video -   

A new series of supercomputer simulations has offered an answer to the mystery of the origins of Saturn’s rings - one that involves a massive collision in the recent history of the 4.5 billion-year-old Solar System.  

According to new research involving NASA and Durham and Glasgow universities, Saturn’s rings could have evolved from the debris of two progenitor icy moons that collided and shattered only a few hundred million years ago.   

They would likely have been similar in size to two of Saturn’s current moons, Dione and Rhea.   

Debris that didn’t end up in the rings could also have contributed to the formation of some of Saturn’s present-day moons.  

Most contemporary high-quality measurements of Saturn have come from the Cassini spacecraft.   

It spent 13 years studying the planet and its systems after entering Saturn’s orbit in 2004.  

The Cassini craft captured precise data by passing by and even diving into the gap between Saturn’s rings and the planet itself.   

Cassini found that the rings are almost pure ice and have accumulated very little dust pollution since their formation, suggesting that they formed during the most recent few per cent of the life of the Solar System. 

Motivated by the remarkable youth of the rings, the research team turned to the COSMA machine hosted by Durham University as part of the UK’s DiRAC (Distributed Research Utilising Advanced Computing) facility.  

The team modeled what different collisions between precursor moons may have looked like.   

These hydrodynamical simulations were conducted using the SWIFT open-source software at a resolution more than 100 times higher than previous studies, giving scientists their best insights into the Saturn system’s history.  

Dr Vincent Eke, Associate Professor in the Department of Physics/Institute for Computational Cosmology, at Durham University, said: “We tested a hypothesis for the recent formation of Saturn’s rings and have found that an impact of icy moons is able to send enough material near to Saturn to form the rings that we see now.  

“This scenario naturally leads to ice-rich rings because when the progenitor moons smash into one another, the rock in the cores of the colliding bodies is dispersed less widely than the overlying ice.” 

Saturn’s rings today live close to the planet, within what is known as the Roche limit – the farthest orbit where a planet’s gravitational force is powerful enough to disintegrate larger bodies of rock or ice that get any closer.   

Material orbiting farther out could clump together to form moons.   

By simulating almost 200 different versions of the impact, the research team discovered that a wide range of collision scenarios could scatter the right amount of ice into Saturn’s Roche limit, where it could settle into rings as icy as those of Saturn today.   

Since other elements of the system have a mixed ice-and-rock composition, alternative explanations haven’t been able to explain why there would be almost no rock in Saturn’s rings.   

Dr Jacob Kegerreis, a Durham University graduate who is now a research scientist at NASA’s Ames Research Center in California’s Silicon Valley, said: “There’s so much we still don’t know about the Saturn system, including its moons that host environments that might be suitable for life, so it’s exciting to use big simulations like these to explore in detail how they could have evolved.”   

Dr Luis Teodoro, of the University of Glasgow’s School of Physics & Astronomy, said: “The apparent geological youth of Saturn’s rings has been a puzzle since the Voyager probes sent back their first images of the planet. This collaboration has allowed us to examine the possible circumstances of their creation, with fascinating results.” 

DiRAC is funded by the UK’s Science and Technology Facilities Council.  

ENDS  

Media Information   

Dr Vincent Eke from Durham University’s Department of Physics is available for interview and can be contacted on v.r.eke@durham.ac.uk.    

Alternatively, please contact Durham University Communications Office for interview requests on communications.team@durham.ac.uk.   

Dr Jacob Kegerreis, a Durham University graduate who is now a research scientist at NASA’s Ames Research Center, California, USA, is available for interview and can be contacted on jacob.kegerreis@durham.ac.uk or  arc-dl-newsroom@mail.nasa.gov.  

Images   

Associated images are available via the following link: https://bit.ly/3LCCmam

Captions 

Simulation01  

A simulation of an impact between two icy moons in orbit around Saturn, ejecting debris that could evolve into the planet's iconic and remarkably young rings. This image shows a 2 km/s impact. Credit: Jacob Kegerreis, Luís Teodoro 

Simulation02

A simulation of an impact between two icy moons in orbit around Saturn, ejecting debris that could evolve into the planet's iconic and remarkably young rings. This image shows a 2 km/s impact with Saturn in the background. Credit: Jacob Kegerreis, Luís Teodoro 

Simulation03 

A simulation of an impact between two icy moons in orbit around Saturn, ejecting debris that could evolve into the planet's iconic and remarkably young rings. This image shows a 3 km/s impact and is a mid-collision snapshot. Credit: Jacob Kegerreis, Luís Teodoro 

Simulation04 

A simulation of an impact between two icy moons in orbit around Saturn, ejecting debris that could evolve into the planet's iconic and remarkably young rings. This image shows a 3 km/s impact. Credit: Jacob Kegerreis, Luís Teodoro 

Video 

Video available via this link: https://www.youtube.com/watch?v=OWaMeUF4enU

The video shows a visualisation of a 3D SPH simulation of colliding icy moons in orbit around Saturn. We find that a wide range of impact scenarios like this could scatter debris far across the Saturn system. This includes a large amount of pure ice heading close to the planet where it could evolve into the famous rings, and even more ice and rock debris that could disrupt other precursor moons in a collisional cascade. 

Source information  

A recent impact origin of Saturn’s rings and mid-sized moons research paper is published in The Astrophysical Journal and can be read via this link: https://doi.org/10.3847/1538-4357/acf4ed 

L.F.A.Teodoro, J.A.Kegerreis, P.R.Estrada, M.´Cuk, V.R.Eke, J.N.Cuzzi, R.J.Massey, and T.D.Sandnes  

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