This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Southwest Research Institute (SwRI) scientists used simulations to understand the role disruptive impacts play on icy moons with subsurface oceans in our solar system. A recent paper published in the journal Nature Astronomy concludes that disruptive impacts can affect the presence and persistence of subsurface oceans in these moons but do not seem to create new oceans.
Many icy moons of the outer solar system are candidate ocean worlds—moons that may harbor large volumes of liquid water under their icy crusts—including several smaller moons of Saturn and Uranus. Curiously, these same moon systems possess characteristics that have led scientists to question whether they are the original moons that formed around their parent planets early in solar system history. Rather, it has been suggested that most or all of the smaller (radius < 1000 km) moons around Saturn and Uranus were disrupted in large collisions.
"For the moons of Saturn, disruptive collisions have been proposed even within the last 100 million years, suggesting that the candidate ocean moons we see today reassembled relatively recently out of the collisional debris of older moons," said Dr. Alyssa Rhoden, a staff scientist in SwRI's Solar System Science and Exploration Division in Boulder, Colorado, and a co-author of the paper. "This proposition led us to question whether reassembled moons still form oceans." To answer this question, the team combined a smoothed particle hydrodynamics (SPH) model to simulate collisions with a thermal-structural evolution model to simulate the evolution of impacted moons.
This combination allowed scientists to compare moons before impact, after impact and without a collision. Disruptive impacts are common, especially during the formative years of the solar system. These impacts would significantly alter the makeup of the moon rather than just leave a crater.
"Our definition of a disruptive impact was that the biggest remaining fragment had to be less than half the size of the initial target," Rhoden said. "So, you are really breaking this thing up." This research considered whether these kinds of impacts played a role in the formation of oceans. "Imagine a moon that is small and frozen and isn't doing anything very interesting.
If you throw something at it and cause a big collision, would that impart enough energy to cause an ocean to form?" Rhoden asked. "Our models indicated that is actually incredibly difficult. 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 study found that overall, large-scale collisions affect only ocean thickness and longevity, but do not contribute to creating new oceans.
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