Astronomers have solved a long-standing mystery surrounding Saturn’s largest moon, Titan, determining it likely formed from a cataclysmic collision between two earlier, similarly sized moons. The finding, published by researchers at the SETI Institute, challenges previous theories that Titan gradually accreted from surrounding material.
The research suggests that a “Proto-Titan,” nearly the size of the current moon, collided with another, smaller moon. The resulting fusion explains Titan’s surprisingly low number of impact craters, a characteristic that has puzzled scientists for years. “This fusion can explain why Titan has surprisingly few impact craters,” researchers stated.
The collision may also account for the origin of Hyperion, Saturn’s largest non-spherical moon. According to the theory, Hyperion could be a fragment ejected during the Titan-forming impact, or it may have coalesced later from debris orbiting Titan.
Further complicating the Saturnian system, recent observations have revealed a significant increase in the number of known moons orbiting the planet. In March 2025, astronomers announced the discovery of 128 new moons, bringing the total to 274 – nearly double the number of moons orbiting all other planets in the solar system combined. These newly discovered moons are slight and irregularly shaped, leading researchers to believe they are fragments from past collisions involving larger moons or comets. Dr. Edward Ashton of the Academia Sinica in Taiwan, the lead researcher on the project, noted the new moons are likely remnants of such events.
Specifically, a cluster named Mundilfari, containing 47 of the newly discovered moons, is believed to have formed from a collision approximately 100 million years ago. This discovery points to a more dynamic and violent past for the Saturnian system than previously understood.
The collision that formed Titan may have also contributed to the formation of Saturn’s rings. Researchers theorize that the impact disrupted Saturn’s inner moons, triggering further collisions that ultimately led to the creation of the rings around 100 million years ago. “Through this event, Titan would have disturbed some of the inner moons, causing more collisions, which some time later, perhaps 100 million years ago, led to the formation of the rings,” said Matija Ćuk, the lead researcher of the SETI Institute study.
Titan is currently drifting away from Saturn at a rate of 11 centimeters per year, faster than previously estimated. This raises questions about the long-term stability of the Saturnian system and whether Titan will eventually be ejected from Saturn’s orbit.
Recent observations from the James Webb Space Telescope (JWST) have added further layers of complexity to the Saturnian puzzle, revealing unexpected features in the planet’s upper atmosphere, including “dark beads” within the auroras and a lopsided star-shaped pattern. These features remain unexplained.
