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. Full image and caption
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, 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."
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 these sites: http://www.nasa.gov/cassini http://saturn.jpl.nasa.gov
Jane Platt
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0880
jane.platt@jpl.nasa.gov
Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
