A UMD-led study found that catastrophic collisions between icy moons barely disturb the hidden oceans beneath their frozen surfaces, offering new insights into life beyond Earth.
Many of the moons orbiting Saturn, Uranus and Neptune likely conceal oceans of liquid water beneath miles of icy shell. Because life as we know it needs water, these buried oceans rank among the most promising places to search for life beyond Earth.
But the outer solar system is akin to a celestial demolition derby. Scientists suspect some of today’s moons are reassembled remnants of earlier generations of moons, shattering and reforming from space debris. One question arises: Do these collisions also destroy a moon’s ocean and with it, any chance for life?
A University of Maryland-led study published on August 21, 2026, in the journal Nature Astronomy offers an answer. After simulating violent collisions on frozen moons, researchers found that even the biggest crashes don’t fundamentally change whether these icy worlds can hold an ocean.
“The big question we asked was whether these destructions help moons have oceans afterward or whether they delete the ocean and reset the moon into a cold, dead world,” explained the study’s lead author Marc Neveu, an astronomy associate research scientist at UMD. “What we found was that those big collisions don't really matter as far as oceans are concerned. If there was an ocean before, there's likely to be an ocean after and vice versa.”
The finding surprised Neveu and his co-authors at the Southwest Research Institute in Colorado and the Weizmann Institute of Science in Israel.
“These simulations were pretty much the biggest collisions we could come up with,” Neveu said. “If those didn’t make a difference, it’s unlikely smaller ones would either.”
In the new study, the researchers connected two very different kinds of computer simulations. One type recreated the violent physics of a cosmic crash, tracking how millions of rock and ice fragments shatter, heat up and clump back together. The other approach simulated the slow burn of a moon’s interior over billions of years, following how heat builds and escapes from the core, and whether ice can melt into an ocean.
Combining these two methods allowed the researchers to follow two sizes of moons, roughly 500 and 1,000 kilometers in radius, as the moons were struck by smaller space rocks, blown apart and reassembled. The team then fast-forwarded through 4.5 billion years of each simulated moon’s afterlife and found that moon sizes played a bigger role than expected in determining a collision’s aftereffects.
“In larger moons, the energy of the crash converts into extra heat that can actually thicken up an existing ocean for a couple billion years. In smaller moons, the story flips,” Neveu said. “Before a collision, these small moons keep a jumbled outer layer of mixed ice and rock that acts like an insulating blanket, helping trap the warmth that sustains an ocean. The impact shakes everything apart, and when the moon re-forms, the rock sinks to the center and the ice floats to the top. It gets harder for the smaller moon to keep an ocean because the blanket’s gone, but in neither case did a collision create an ocean that would’ve otherwise stayed frozen.”
The team’s findings apply to a whole family of real worlds that NASA and other space agencies plan to investigate, including Saturn’s mid-sized moons Mimas, Enceladus, Tethys, Dione and Rhea; the moons of Uranus, including Miranda, Ariel, Umbriel, Titania and Oberon; and Neptune's large moon Triton. One of Saturn’s moons, Rhea, already caught the team’s attention as a possible test case because its ancient craters look strangely smooth and softened—almost as if warmed from within.
“It’s like building a snowman in the winter, and then a week later, there’s been warming and sunlight so the snowman is melting away,” Neveu explained. “Rhea’s craters look smoothed out like that, but it wasn’t the sun. The heat came from below. A long-ago collision that boosted an interior ocean could help explain why the moon appears that way.”
The team’s results offer new insight as NASA and the planetary science community weigh future missions to these icy worlds. Knowing which moons are most likely to harbor water could help decide where to send spacecraft and what to look for, from the gravitational fingerprint of a hidden ocean to salty deposits and icy “cryovolcanoes” on the surface. It even shapes how sensitive life-detecting instruments need to be.
“If there's only a handful of microbes, you won’t be designing the same kind of search mission as you would if the ocean were full of whales,” Neveu said. “The type of life we’re looking for will determine what kind of tools we need to develop.” Still, he cautioned that a moon's collision history is just one factor shaping its potential to host life. Others, like the heat generated by tides, matter at least as much.
For Neveu, the study is one piece of a much bigger puzzle that includes how tides heat these planetary oceans and how shifting moon orbits set them on collision courses in the first place.
“Down the line, I would love to press play on a moon system and watch how the moons move, how they smash into each other and how their interiors change as a result,” Neveu said. “Maybe then we can reconstruct what happened around Saturn, Uranus and Neptune.”
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The study, “The role of disruptive impacts on ocean generation and longevity in icy moons,” was published in Nature Astronomy on August 21, 2026.
This research was funded by NASA's Habitable Worlds program (Award No. 80NSSC22K0403) with additional support from a NASA Hubble Fellowship (Award No. HST-HF2-51491) and NASA's Goddard Space Flight Center (Award No. 80GSFC24M0006). This article does not necessarily reflect the views of this organization.
