[meteorite-list] NASA Cassini Images May Reveal Birth of New Saturn Moon

[Ron Baalke]

April 14, 2014
     
NASA Cassini Images May Reveal Birth of New Saturn Moon

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 narrow angle camera 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 (April 14, 2014) 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, and 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 see in images so far.  
Scientists estimate it is probably no more than about a half mile 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 comprised 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 (JPL) 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."

The Cassini-Huygens mission is a cooperative project of NASA, the European  
Space Agency and the Italian Space Agency. JPL, a division of the California  
Institute of Technology, manages the mission for NASA's Science Mission  
Directorate in Washington.

To view an image of the Saturn ring disturbance attributed to the new moon,  
visit:

http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18078 

For more information about Cassini, visit:

http://www.nasa.gov/cassini 

-end-

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov 

Jane Platt
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0880
jane.platt at jpl.nasa.gov