Saturn’s largest moon, Titan, may have a surprisingly violent origin story. A new study suggests that this massive moon wasn’t formed gradually over billions of years, but rather from a cataclysmic collision between two earlier, similarly sized moons approximately , researchers proposed. This collision may also explain the formation of Saturn’s iconic rings and the unusual orbits of other Saturnian satellites.
Titan is the second-largest moon in our solar system, trailing only Jupiter’s Ganymede. It measures roughly in diameter, making it about 1.5 times wider than Earth’s moon and approximately 5% larger than the planet Mercury.
What sets Titan apart from many other moons is its dense atmosphere, composed primarily of nitrogen and 1.5 times thicker than Earth’s. It’s also the only other body in our solar system, besides Earth, confirmed to have liquid on its surface – in this case, methane lakes and rivers – making it a compelling location in the search for extraterrestrial life. The European Space Agency’s Huygens probe successfully landed on Titan in , marking the only landing on a moon other than our own.
Saturn’s Missing Moon
Until recently, the prevailing theory was that Titan, like most moons, formed through the gradual accretion of dust and rock over billions of years. However, data collected by NASA’s Cassini probe, which extensively studied Saturn and its moons, prompted researchers to reconsider this model. The new study, uploaded to the preprint server arXiv and accepted for publication in The Planetary Science Journal, proposes a different scenario.
Researchers at the SETI Institute, led by Matija Ćuk, propose that Titan formed around when two large moons, dubbed “Proto-Titan” and “Proto-Hyperion,” collided. This impact not only created Titan but also likely birthed another Saturnian moon, Hyperion, from the debris of the collision – a process similar to how scientists believe Earth’s moon formed after a collision with a Mars-sized object called Theia approximately .
This collision could also explain several other puzzling features of the Saturnian system. Saturn’s orbital tilt and the unusual orbits of moons like Iapetus and Rhea suggest a past gravitational disturbance, potentially caused by a now-destroyed moon. The researchers theorize that this missing moon didn’t simply disappear but was instead shattered in the collision that formed Titan and Hyperion.
The team’s analysis suggests that Hyperion, approximately 84 miles (135 km) in diameter, is a direct result of the collision. The moon is locked in an orbital resonance with Titan, circling Saturn three times for every four of Titan’s orbits. According to Ćuk, “We recognized that the Titan-Hyperion lock is relatively young, only a few hundred million years old. This dates to about the same period when the extra moon disappeared. [So] perhaps Hyperion did not survive this upheaval but resulted from it.”
Rings, Orbits, and Automobiles
The implications of this collision extend to Saturn’s magnificent rings. The researchers propose that the impact generated debris that eventually settled into the ring system approximately 100 million years ago. This hypothesis offers a potential explanation for the surprisingly young age of the rings, which has been a long-standing mystery. The collision and subsequent orbital disruptions could have sent material spiraling inward, forming the iconic rings we observe today.
the impact may explain the peculiar orbits of Iapetus and Rhea, which are significantly tilted compared to other Saturnian moons and exhibit a resonance with Titan’s orbit. The gravitational chaos resulting from the collision could have perturbed the orbits of these moons, leading to their current configurations.
Titan’s lack of impact craters is another puzzle piece that fits into this new model. Because the moon is relatively young – formed only around 400 million years ago – it has had less time to accumulate craters from meteoroid impacts. Prior to the collision, Proto-Titan may have been heavily cratered, similar to Jupiter’s moon Callisto.
NASA’s upcoming Dragonfly mission, scheduled to launch in and arrive at Titan in , could provide crucial evidence to test this hypothesis. The drone-like spacecraft will explore Titan’s surface, searching for geological or chemical signatures of a massive ancient moon-moon collision. The mission aims to analyze the composition of Titan’s surface and subsurface, potentially revealing remnants of the impact event and shedding light on the moon’s formation and evolution.
