Giant Collisions May Actually Destroy Alien Oceans Instead Of Creating Them

High-energy impacts in the outer reaches of the Solar System, once thought to be potential catalysts for the formation of hidden subsurface oceans, may actually be detrimental to the existence of liquid water on icy moons. New computational modeling indicates that the heat generated during catastrophic collisions dissipates too rapidly to sustain the liquid environments previously theorized to exist beneath frozen crusts.

The study, published in Nature Astronomy, challenges prevailing assumptions about how moons orbiting giants like Saturn and Uranus maintain their internal heat. While scientists have long speculated that massive impacts could melt icy interiors, the research team at the Southwest Research Institute (SwRI) found that the reality is far more restrictive.

Collisions as Geological Transformers Rather Than Ocean Builders

To determine how violent events alter the evolution of moons, the researchers utilized sophisticated simulations that track both the physics of planetary impacts and the subsequent thermal and structural changes over long durations. The modeling revealed that while a major collision can fundamentally reorganize a moon’s internal architecture, it rarely produces the stable, long-term conditions required for an ocean.

Dr. Alyssa Rhoden, a staff scientist at SwRI and co-author of the work, noted that the expectation that energy transfer would foster ocean formation is often unsupported by the data. “Our models indicated that is actually incredibly difficult,” Rhoden explained. “Most of the time a small moon experiencing a disruption may lose its ocean or prevent an ocean from forming in the first place.”

The Thermodynamic Hurdle for Small Worlds

When an icy moon is shattered by a collision and subsequently reassembles, the resulting body often undergoes internal differentiation. During this phase, heavier rocky material migrates toward the center, while ice accumulates toward the surface. While this process can create a more substantial rocky core, it does not trap the heat necessary to keep water in a liquid state.

Dr. Raluca Rufu, who collaborated on the study, explained that the physics of cooling plays a critical role. “Introducing more energy to the system could melt the ice and create oceans, but this energy dissipates very quickly, which actually works against forming oceans,” Rufu stated. She likened the process to heating fragmented food; because the surface-area-to-volume ratio increases, the fragments lose their thermal energy at a rate that prevents a cohesive, lasting internal ocean from developing.

Size Constraints on Ocean Preservation

The research emphasizes a clear size-dependent threshold for survival. While moons with a radius of 1,000 kilometers or larger possess enough gravitational and thermal inertia to potentially retain an existing ocean through a disruptive event, smaller bodies are significantly more vulnerable.

In smaller moons, the post-collision reassembly leads to a thicker icy crust, effectively sealing off the interior from the conditions required for liquid water. As investigators continue to map the complex history of the outer Solar System, this new understanding of collision dynamics provides a more realistic framework for evaluating which moons may be genuine candidates for subsurface oceans and which were likely “reset” by the violent history of their orbits.