Saturn Just Birthed a Baby Moon. How Does that Happen?

Wednesday, April 16, 2014

The planet Saturn is seen backlit by the sun, sent Cassini spacecraft July 19, 2013 in space. NASA unveiled the image, that spans 404,880 miles across. November 12, 2013 (NASA/JPL-Caltech/SSI/Getty)

We’ve heard about stars dying, but what about new moons being born?

Saturn used to have 62 known moons, most of which are quite small—until now. The ringed giant added one more satellite to that count, a little icy rock that NASA has named “Peggy.”

Peggy revealed herself in images NASA received from the Cassini spacecraft (pictured below), the space organization announced yesterday. More startlingly, the photographs revealed Peggy’s birth, as its icy mass seemed to emerge off of Saturn’s outer A ring. Tariq Malik, the managing editor of, discusses the discovery.

"Peggy, if it is actually a full moon, is pretty small—about half a mile wide, maybe half a New York City block," says Malik. "It's cold and icy, and it could already be falling apart. But it does show that moons may still be forming around planets in our solar system."

According to Malik, scientists believe that Peggy is a moon forming from the material that surrounds Saturn. The process mirrors how Earth's moon formed, says Malik, who adds that the planets in our solar system also formed from material that surrounded the Sun. 

"They have this photo (pictured below) of ripples in Saturn's rings of stuff coming together; a big clump of stuff right on the edge of the rings that could just pop free and be its own moon if it gets enough mass for it," he says.

Malik says that over millions of years, bits of space particles make contact and get larger. As these space bits get lager, they assume a higher gravity and are able to attract more space particles and get even bigger over time—a process that Peggy is likely experiencing.  

"(Scientists) haven't seen the object itself—they can only see the ripples of it and this kind of clumping arch in the rings of Saturn right on the very edge," says Malik. "What they hope is that they're going to be able to get closer in the next couple years and actually see the object itself to see if it's an actual moon, if it could escape to actually become a full fledged moon, or if it's going to break apart or stay where it is."

The rings of Saturn have puzzled astronomers since Galileo. Some believe that Saturn's rings were once a planet unto their own, while others speculate that the rings formed because something hit the planet. Malik says that a predominate theory today is that Saturn's rings were once quite bigger than what we see nowadays, and that Saturn's 62 moons all formed from the planet's larger rings that no longer exist today.

"That's why scientists thought this moon formation plan, from the rings that came from that either big collision or extra material left from Saturn, was finished," he says. "So seeing an active process now, if that's what is happening and it seems like it might be, is really exciting."

Click here to read the full announcement from NASA's Jet Propulsion Laboratory.

The disturbance visible at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft results from gravitational effects on ring particles by an object that may be replaying the birth process of icy moons. Cassini's narrow-angle camera recorded this view on April 15, 2013.


Tariq Malik

Produced by:

Seth Maxon


T.J. Raphael

Comments [2]

Larry Fisher from Brooklyn, N.Y.

Saturn mooning us!

Apr. 16 2014 02:02 PM

Can't say I know much about the evolution of planets, but it makes sense that the rings are slowly being absorbed into the planet. Obviously, there's gravity being applied just as on earth, and once something in the upper atmospheres of Saturn gains enough mass it will begin coming down.

Certainly is fascinating, and we don't usually think of the planets as changing, and evolving. Many people here on earth don't want to believe we are in the process of evolution, continuously, of the planet and its inhabitance in quite dynamic ways.

This is a good lesson - thanks!

Apr. 16 2014 12:43 PM

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