Astronomers say they have solved one of Saturn’s greatest mysteries

Saturn’s largest moon, Titan, is one of the solar system’s oddities. Now, researchers have unlocked key insights about this mysterious moon, including how it came to be. The answer may also shed light on the origin of Saturn’s beautiful rings.

Shrouded in a thick haze, Titan is about half the size of Earth and even larger than Mercury — so massive that its gravitational pull makes Saturn wobble and tilt. Titan is also moving away from Saturn at a rate of 11 centimeters (4.3 inches) a year, far faster than astronomers previously thought. Eventually, the moon could be ejected from its orbit entirely.

But Titan’s drifting orbit is just one of many puzzles that astronomers are trying to solve about Saturn and some of its 274 moons. Many of the questions have arisen from data collected by Cassini, a spacecraft that explored the Saturnian system from 2004 to 2017.

New research has combined previous theories of Titan’s formation, data from Cassini and computer simulations to suggest a novel origin story for Saturn’s largest moon. The study was published this month on the open-access repository ArXiv and accepted for publication in The Planetary Science Journal.

“In this paper, I tried to put all these things together, and I propose that there was an extra moon about half a billion years ago that collided with Titan, that actually became part of Titan,” said lead author Matija Ćuk, a research scientist at the SETI Institute in Mountain View, California. SETI is a nonprofit organization that explores topics such as planetary science, the origin of life and extraterrestrial intelligence.

The collision could also have produced Hyperion, the largest of Saturn’s nonspherical moons, which is far smaller than Titan at about 5% of its diameter. According to this theory, Hyperion could either be a fragment that resulted from the collision between Titan and the lost moon, or it may have formed later from debris that accumulated around Titan’s orbit.

The merger between Titan and the lost moon could also have led to the formation of Saturn’s rings, Ćuk added. “From this event, Titan could have perturbed some of the inner moons into more collisions, which created the rings sometime later, maybe 100 million years ago,” he said.