![]() ![]() Rhoden suspects the moon’s global ocean could provide insight into its ice formations. “This is a big mystery and an area of active research now,” Beuthe said. Scientists have explored whether an impact event may have cracked Enceladus’s shell or whether a tidal process thinned the ice gradually over time. An Evolving OceanĮnceladus’s peculiar ice patterns are among the most intriguing puzzles for planetary scientists to solve: Why is the ice on Enceladus’s north pole so much thicker than the ice on its south pole? How did the series of cracks observed along the moon’s equator form? “There are a lot of things we don’t know and have to clear up to understand these worlds,” Beuthe said, referring to all of the icy moons of Saturn and Jupiter. It’s possible that it could be weak or porous, filled with debris from Saturn’s rings rather than made up completely of water ice. At the same time, he acknowledged that researchers don’t know the resistance of Enceladus’s ice in real conditions. ![]() According to Beuthe, who was not involved with the new research, the forces Rhoden and her team modeled are very small, smaller than the typical yield strength of pure ice seen in the lab. Mikael Beuthe, a researcher at the Royal Observatory of Belgium, remained cautious about the results. “When you hit that breaking point, you get the right orientations,” Rhoden said. But by simulating ice cracking at its failure strength, rather than at the maximum point of pressure, Rhoden and her colleagues were able to accurately model the features. ![]() Previous studies that focused on what happened to ice at the point of the strongest tidal stress often created fractures, but the simulations could not point the tiger stripes in the appropriate direction. “When it breaks, it doesn’t matter how much you would or could have pulled it it only matters what the failure strength of the rubber band was,” said Rhoden.īy simulating the ice cracking at its failure strength, rather than at the maximum point of pressure, researchers were able to re-create Enceladus’s tiger stripes in computer simulations. Rhoden compared Enceladus’s icebreaking process to stretching a rubber band until it snaps. Ice at the northern pole most likely reaches a thickness of more than 10 kilometers, preventing it from breaking. They found that the ever present tugs created stripes most effectively when the ice at the southern pole was less than 5 kilometers thick. Rhoden and her colleagues modeled a variety of icy shell structures to see how they would react to the pull of lunar tides. But even when the moons don’t line up, Enceladus continues to feel their presence through tidal stresses. These tidal stresses can dramatically increase when the moons reach specific alignments, exerting a powerful tug on Enceladus’s icy shell. “You have to have a reason that you don’t see it at the north pole.” Different StressesĪs Enceladus orbits Saturn, it experiences a gravitational pull not only from the giant planet but also from its fellow moons. “One of the challenges of Enceladus is, if you can make fractures at the south pole with low stress, you should make fractures at the north pole with the same stress,” said first author Alyssa Rhoden, a planetary scientist at the Southwest Research Institute in Colorado. The new study considers the breaking point of the ice itself. Those studies focused on what happened when gravitational tugs on the moon were at their strongest. But previous studies have failed to simulate the formation of cracks that resemble the tiger stripes. Observations from Cassini revealed that the moon’s ice is thicker around the equator and thinner at the poles, especially the southern pole. The idea of thinner ice around the southern pole is certainly not new. ![]()
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