NASA Uncovers Mystery Behind Saturn’s ‘Odd Little’ Moons

NASA's Cassini spacecraft's closest-ever flybys across Saturn provided the space agency with new information about the planet’s five tiny moons. The mission found that all of the natural satellites are actually covered with material from the planet's rings as well as the icy particles coming from Saturn's larger moon Enceladus. 

The findings, published in the journal Science, used data collected by Cassini's instruments before the spacecraft’s mission ended in 2017. It showed that the five moons have surfaces that are highly porous which make their shape appear blobby and ravioli-like unlike Earth’s moon that appears spherical, NASA said in a statement

Cassini’s mission confirms that Saturn’s natural satellites were formed in multiple stages as the planet’s ring material settled onto denser cores, which scientists suspect to be remnants of a larger object that broke apart.

"The daring, close flybys of these odd little moons let us peer into how they interact with Saturn's rings," Bonnie Buratti, author of the study and an expert at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in the statement. "We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators."

The surfaces of those closest moons to Saturn, named Daphnis and Pan, were found to be the most altered by the ring material. The other satellites Atlas, Prometheus and Pandora, with distances farther from the planet, also have the ring material but are covered with icy particles and water vapor from the plume spraying out of Enceladus.

Cassini Flybys

The spacecraft conducted its closest mission around the ring moons between December 2016 and April 2017. Cassini looked into the electromagnetic spectrum, the ring’s dust, plasma and magnetic fields.

NASA ended the mission in September 2017 after the spacecraft signalled low fuel. Mission controllers then sent Cassini into Saturn's atmosphere. 

Two years after putting Cassini to rest, NASA said more information are still coming from the spacecraft’s last orbits, called the Grand Finale. The agency plans to publish new findings in the coming months. 

Cassini was launched under a joint project between NASA, the European Space Agency and the Italian Space Agency. NASA's JPL designed, developed and assembled the Cassini orbiter and managed the mission.