Astronomers have long speculated that our solar system might have originally hosted a third ice giant. Recent research offers intriguing hints that the moons of Jupiter and Uranus could point towards this lost world. Evidence indicates that around 3 to 4 billion years ago, the larger planets were much closer to each other and the sun than they are today. Over time, the gravity of these planets likely interacted, causing them to shift into their current positions.
Researchers ran simulations to see how this celestial juggling affected the moons of Jupiter and Uranus. The findings suggest that the moons of these two gas giants survived a chaotic time thanks to the presence of a now-vanished ice giant.
Matthew Clement and his team used computer simulations involving 122 potential early solar systems, varying the number of planets and their respective migrations. They wanted to see which setups could recreate the outer solar system we see today. The focus was on the moons of Jupiter and Uranus, which are vital to understanding these scenarios. In their paper, Clement notes that the gravitational encounters between planets have played a significant role in shaping our solar system.
Past research on asteroids and other small celestial bodies has helped scientists piece together how giant planets might have influenced their orbits. Jupiter’s moons, for instance, are locked in a unique orbital pattern, while their craters indicate they are ancient.
Interestingly, the survival odds for these moons during the time of migrating giants were low—less than 15% for Jupiter’s moons and just 9% for Uranus’s. Scenarios that favored the survival of one set of moons typically hindered the other. Only a 1% chance existed for both to survive the same situation, indicating how rare their current configuration is.
In the most likely scenario, the solar system started with five giant planets, including an additional ice giant. When Jupiter moved closer to this ice giant, it might have sent the latter into interstellar space. Although this ejected ice giant didn’t directly save the other moons, its existence seems to have affected the trajectories of the remaining planets and their moons.
Notably, the simulations showed that even during tumultuous periods, Jupiter’s moons were more likely to remain intact due to their arrangement. In contrast, Uranus’s moons likely faced two significant upheavals: one from a large impact that tilted Uranus on its side and another from the migration of the larger planets.
Despite exploring various configurations, the simulations reveal that reconstructing the exact sequence of events that led to our solar system today is extremely challenging. Clement and his colleagues emphasize that while it’s probable none of their simulations match reality precisely, they provide a clearer idea of a likely scenario. The study, published in the journal Icarus, hints at the intriguing possibility of a long-lost ice giant drifting through the cosmos.
