NASA Cassini images may reveal birth of a Saturn moon

Apr 15, 2014 by Jane Platt
NASA Cassini images may reveal birth of a saturn moon
The disturbance visible at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft could be caused by an object replaying the birth process of icy moons. Credit: JPL/NASA

(Phys.org) —NASA's Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn that may be a new moon, and may also provide clues to the formation of the planet's known moons.

Images taken with Cassini's on April 15, 2013, show disturbances at the very edge of Saturn's A ring—the outermost of the planet's large, bright rings. One of these disturbances is an arc about 20 percent brighter than its surroundings, 750 miles (1,200 kilometers) long and 6 miles (10 kilometers) wide. Scientists also found unusual protuberances in the usually smooth profile at the ring's edge. Scientists believe the arc and protuberances are caused by the gravitational effects of a nearby object. Details of the observations were published online today by the journal Icarus.

The object is not expected to grow any larger, and may even be falling apart. But the process of its formation and outward movement aids in our understanding of how Saturn's icy moons, including the cloud-wrapped Titan and ocean-holding Enceladus, may have formed in more massive rings long ago. It also provides insight into how Earth and other planets in our solar system may have formed and migrated away from our star, the sun.

"We have not seen anything like this before," said Carl Murray of Queen Mary University of London, the report's lead author. "We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right."

The object, informally named Peggy, is too small to be seen in images so far. Scientists estimate it is probably no more than about a half mile (about a kilometer) in diameter. Saturn's icy moons range in size depending on their proximity to the planet—the farther from the planet, the larger. And many of Saturn's moons are composed primarily of ice, as are the particles that form Saturn's rings. Based on these facts, and other indicators, researchers recently proposed that the icy moons formed from ring particles and then moved outward, away from the planet, merging with other moons on the way.

"Witnessing the possible birth of a tiny moon is an exciting, unexpected event," said Cassini Project Scientist Linda Spilker, of NASA's Jet Propulsion Laboratory in Pasadena, Calif. According to Spilker, Cassini's orbit will move closer to the outer edge of the A ring in late 2016 and provide an opportunity to study Peggy in more detail and perhaps even image it.

It is possible the process of moon formation in Saturn's rings has ended with Peggy, as Saturn's rings now are, in all likelihood, too depleted to make more moons. Because they may not observe this process again, Murray and his colleagues are wringing from the observations all they can learn.

"The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons," Murray said. "As the moons formed near the edge, they depleted the rings and evolved, so the ones that formed earliest are the largest and the farthest out."

Explore further: Join in the Cassini name game

More information: Carl D. Murray, Nicholas J. Cooper, Gareth A. Williams, Nicholas O. Attree, Jeffrey S. Boyer, The discovery and dynamical evolution of an object at the outer edge of Saturn's A ring, Icarus, Available online 28 March 2014, ISSN 0019-1035, dx.doi.org/10.1016/j.icarus.2014.03.024.

add to favorites email to friend print save as pdf

Related Stories

Join in the Cassini name game

Apr 11, 2014

As NASA's Cassini mission approaches its 10th anniversary at Saturn, its team members back here on Earth are already looking ahead to an upcoming phase.

Image: Infrared image of Saturn's rings

Jan 22, 2014

(Phys.org) —Although it may look to our eyes like other images of the rings, this infrared image of Saturn's rings was taken with a special filter that will only admit light polarized in one direction. ...

Saturn's little wavemaking moon

Apr 25, 2013

Captured on January 15, this narrow-angle Cassini image shows an outer portion of Saturn's A ring on the left and the ropy F ring crossing on the right. The thin black line near the A ring's bright edge is ...

The rings on the planet go 'round and 'round...

Dec 24, 2012

Recently I posted an image of two of Saturn's shepherd moons, Pandora and Prometheus, captured by Cassini in a face-off across the spindly F ring. Now here's a much wider-angle view of the gas giant's rings, ...

Image: Quintet of moons

Nov 05, 2013

(Phys.org) —Five moons pose for the international Cassini spacecraft to create this beautiful portrait with Saturn's rings.

Space Image: Rings, Titan and Enceladus

Apr 19, 2012

Saturn’s icy moon Enceladus hangs below the gas giant’s rings while Titan lurks in the background, in this new image taken by the Cassini spacecraft.   Faint detail of the tiger stripe mark ...

Recommended for you

SDO captures images of two mid-level flares

Dec 19, 2014

The sun emitted a mid-level flare on Dec. 18, 2014, at 4:58 p.m. EST. NASA's Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts ...

Why is Venus so horrible?

Dec 19, 2014

Venus sucks. Seriously, it's the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you ...

Image: Christmas wrapping the Sentinel-3A antenna

Dec 19, 2014

The moment a team of technicians, gowned like hospital surgeons, wraps the Sentinel-3A radar altimeter in multilayer insulation to protect it from the temperature extremes found in Earth orbit.

Video: Flying over Becquerel

Dec 19, 2014

This latest release from the camera on ESA's Mars Express is a simulated flight over the Becquerel crater, showing large-scale deposits of sedimentary material.

Spinning up a dust devil on Mars

Dec 19, 2014

Spinning up a dust devil in the thin air of Mars requires a stronger updraft than is needed to create a similar vortex on Earth, according to research at The University of Alabama in Huntsville (UAH).

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.