Astronomers say they’ve finally unraveled one of Saturn’s biggest long-standing mysteries.

By Muhammad MubashirPublished On 24 Feb 2026

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.

A false-color view of Saturn's moon Hyperion, obtained during Cassini's flyby in September 2005.

NASA/JPL/Space Science Institute

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.

An extra moon ‘explains everything’

The researchers found telltale signs of an ancient collision in Saturn’s tilt, which is made obvious by its rings; the gas giant rotates at an angle of 26.7 degrees compared with the plane at which it orbits the sun.

Saturn's rings are tilted about 26.7 degrees relative to the planet's orbital plane.

NASA/JPL-Caltech/Space Science Institute

Before Cassini’s mission, astronomers believed that gravitational disturbances inflicted by neighbor Neptune’s orbit caused Saturn’s tilt over time.

“The orbit of Neptune has a bit of a wobble in space,” Ćuk said. “The orbits of planets are huge and have huge energy. But the spins of planets are much, much smaller, so if you connect these two motions — the orbit of Neptune and the spin of Saturn — it is the spin of Saturn that will change.”

However, Cassini’s data showed that the two planets are not exactly in sync, pointing to a missing element. In 2022, astronomers suggested that a lost moon, which they named Chrysalis, was a probable explanation for Saturn’s current tilt. It once orbited the planet, for billions of years, contributing to Saturn’s resonance with Neptune, but around 160 million years ago the moon came too close to Saturn and was pulled apart in an event that created the planet’s rings and shifted its tilt.

Ćuk and his colleagues refined that idea. They hypothesize that the event was not just a moon grazing Saturn and then disintegrating but a collision between predecessors of both Titan and Hyperion. “I call it proto-Hyperion, but it was 1,000 times larger — it was like a smaller version of Titan,” Ćuk said.

This lost moon collided with Titan and lost much of its mass, an event that would explain Titan’s drifting orbit and Saturn’s spin. “Right now, Saturn is wobbling a little bit too fast,” Ćuk said. “But if you go back a few hundreds of millions of years when we saw this happen, the wobble was just short of what we needed to have the resonance with Neptune. And if you add an extra moon, you make it exact. And that explains everything.”

In other words, the gravity and mass of the lost moon kept Saturn and Neptune in sync, and only its disappearance explains why they are now slightly misaligned.

If the collision also created Hyperion in its current form — a smaller, tumbling, misshapen rock — it would explain why its orbit is locked with Titan’s. But it remains unclear, Ćuk said, whether Hyperion is a fragment of Titan’s precursor or of the lost moon that merged with it.

According to the study, Saturn’s rings could have formed hundreds of millions of years after the event. Titan’s expanding orbit interacted with some of Saturn’s inner moons, disturbing them to the point of making them smash into each other. Some of the resulting debris survived as the rings.

A paper published in February, which postulates that Titan’s surface is as young as 300 million years old based on the lack of impact craters, lends credibility to the collision scenario, according to Ćuk.

But the best way to test the theory is using NASA’s Dragonfly — a nuclear-powered, car-size rotorcraft that will fly over Titan’s surface and land in different spots to collect and analyze samples with its onboard instruments. It is currently scheduled to launch in 2028 for arrival on Titan by late 2034.

Dragonfly, seen here in an artist's concept, is set to be able to land on Titan's surface.