Seeker Archives

Are Saturn's Moons and Rings Younger Than the Dinosaurs?

Some of the moons and icy objects orbiting Saturn may have formed less than 100 million years ago, while dinosaurs still roamed the Earth.

Saturn's Moons and Rings Younger Than the Dinosaurs?

Some of the moons and icy objects orbiting Saturn may have formed less than 100 million years ago, while dinosaurs still roamed the Earth.

The idea that some of Saturn's moons may be relatively modern stems from computer models that simulated the moons' gravitational interactions and shifting orbital tilts over time.

ANALYSIS: Fog Detected on Surface of Saturn Moon Titan

SETI Institute astronomer Matija Cuk and colleagues conclude that the moons inferior to giant Titan are not primordial, and most likely formed in the last 2 percent of the planet's 4.5 billion-year history.

Saturn hosts at least 62 moons, 53 of which are currently named. The tally doesn't include the hundreds of small icy objects that comprise the planet's rings.

Titan, Saturn's largest moon (which is bigger than the planet Mercury), is the only moon in the solar system that has a thick atmosphere.

PHOTO: Saturn Moons Align (Almost) to Perfection

Though most of Saturn's current moons may be relatively new, the models show the planet has always had hordes of orbital companions.

"Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn's motion around the sun. Eventually, the orbits of neighboring moons crossed and these objects collided. From this rubble, the present set of moons and rings formed," Cuk said in a statement.

The research is published in The Astrophysical Journal.

A grand canyon called Ithaca Chasma cuts across the fact of Saturn’s moon Tethys in this image from NASA’s Cassini probe. Scientists think the canyon opened millions of years ago when Tethys was orbitally synced with sister moon Dione.

Something is erasing craters on several moons of Saturn. And here's the neat thing -- it's likely a different process for each moon studied, according to the authors who developed a model for it. The results are published

in a new Icarus paper

called "Surface ages of mid-size Saturnian satellites" led by Romina Di Sisto (part of the faculty of astronomy and geophysics at Universidad Nacional in Argentina). The authors compared their theoretical predictions with "crater counts" (from other scientists) of Cassini and Voyager images of several Saturn satellites and concluded there are fewer smaller craters than predicted. Here are some of the most likely crater-erasing processes on several moons of Saturn. The authors plan to continue their work with Titan and other Saturnian moons in the future.

There are geysers regularly erupting from Enceladus,

particularly from four parallel fractures

("tiger stripes") near the south pole, according to a 2006 study. Craters would be erased both by the plumes and some tectonic activity.

Some of the material escapes Enceladus

and populates Saturn's E ring, while the rest falls back on to the surface and erases craters, according to a 2010 study.

While Iapetus has an old surface, astrophysicists have noticed that the leading side of the moon is dark, while the trailing side is brighter. While it's unclear what is causing this difference, some theories include internal processes or perhaps debris or dust material falling from other moons of Saturn, to the darker side of Iapetus. In 2010, a study

suggested that both processes

may be at work at once if the dark material is falling on the leading hemisphere, triggering a runaway global dispersement of water ice.

A team of researchers

looked for plumes on Mimas

and said in 2011 that their search was in vain, according to Di Sisto. Therefore, there must be some sort of lower-level geologic activity that is reshaping the surface. Since Mimas is among the moons that could have an icy subsurface ocean, perhaps there is something related to that in the interior causing the crater erasure on the outside, Di Sisto's team suggests.

In the same study that looked at Mimas in 2011, the scientists of that study also

concluded that Tethys has no plumes

. When looking at Tethys in far ultraviolet light, a weird picture emerges; its leading hemisphere is brighter than the trailing hemisphere, according to Di Sisto. Also, its surface appears strangely porous. Perhaps it is being pummeled with material from Saturn's E ring. Or, there could be geologic activity that hasn't yet been detected by Cassini.

Dione also appears bereft of plumes

, at least when looking for vapor production that is too orders of magnitude smaller than what has been observed on Enceladus. "However, plume activity cannot be absolutely ruled out because it can be under the detection limit," Di Sisto wrote. Like Tethys, Dione is also brighter on its leading hemisphere than its trailing one. While Di Sisto did not suggest what process could be causing the craters to erase, Di Sisto did point out that Dione has a tenuous atmosphere (

as per a separate 2011 study

.)

A couple of neat things about Rhea -- a 2010 study found it has a

tenuous atmosphere of oxygen and carbon dioxide

that may be created by surface water ice decomposing due to radiation from plasma (ionized gas) from Saturn's magnetosphere. Also, that

plasma appears to affect the surface

, a 2012 study concludes. This could account for why small craters are erased on the surface of Rhea, Di Sisto suggests.