Saturn’s rings may be birthing a new moon:

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.

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
Image Credit: NASA/JPL-Caltech/Space Science Institute

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

For more information about Cassini, visit: www.nasa.gov/cassini

The ESA/NASA Cassini Mission investigating the Saturn system has detected a large body of liquid water below a thick crust of ice on the moon Enceladus:

Icy moon Enceladus has underground sea

Saturn’s icy moon Enceladus has an underground sea of liquid water, according to the international Cassini spacecraft.

Inside Enceladus

Understanding the interior structure of 500 km-diameter Enceladus has been a top priority of the Cassini mission since plumes of ice and water vapour were discovered jetting from ‘tiger stripe’ fractures at the moon’s south pole in 2005.

Subsequent observations of the jets showed them to be relatively warm compared with other regions of the moon and to be salty – strong arguments for there being liquid water below the surface.

But planetary scientists have now been able to investigate the interior of the enigmatic moon directly, using Cassini’s radio science experiment.

Enceladus plumes

On three separate occasions in 2010 and 2012, the spacecraft passed within 100 km of Enceladus, twice over the southern hemisphere and once over the northern hemisphere.

During the flybys, Cassini was pulled slightly off course by the moon’s gravity, changing its velocity by just 0.2–0.3 millimetres per second.

As tiny as these deviations were, they were detectable in the spacecraft’s radio signals as they were beamed back to Earth, providing a measurement of how the gravity of Enceladus varied along the spacecraft’s orbit. These measurements could then be used to infer the distribution of mass inside the moon.

Enceladus’ craters and complex, fractured terrains