Lurking in the shadows of our solar system's gas and ice giants are small, frozen moons. Some of these moons contain swirling oceans of liquid water surrounded by a solid shell of ice.
New research published in Natural astronomy, cracked the surface of these moons and showed what might be happening in the depths of their oceans, which are considered excellent candidates for hosting extraterrestrial life.
“Not all of these moons are known to have oceans, but we know that some do. We're interested in the processes that shape their evolution over millions of years, and that allows us to think about what the surface expression of the ocean world would be,” said Max Rudolph, an Earth and planetary scientist at the University of California, Davis, in his paper. press release.
Icy moons of the solar system
Instead of magma flowing, geological shifts occur. icy moons formed by melting ice. The icy shells covering these moons grow and shrink in response to forces generated by the planet they orbit and neighboring moons, which heat or cool these shells.
While Rudolph led the researchers, his team used mathematical models to analyze what happens when the ice sheet melts. The team found that warming ice sheets reduce pressure on the Moon as dense ice melts into water.
Their calculations showed that if moon small enough, this fall could be enough to reach the “triple point” where ice, water and water vapor could be present on the Moon. In short, the frozen oceans will begin to boil. Moons small enough for this to happen include Uranus' moon Miranda, and Saturn's moons Mimas and Enceladus.
Read more: Latent heat on Saturn's icy moon could help support life
Probe images support ice analysis
Data from space probes also support this theory. Voyager 2, which flew past Miranda in 1986, captured images of the coronae, the distinctive rocks and valleys that scar the lunar surface. According to the authors, these traces could have formed in boiling oceans.
On Mimas, a tiny, cratered moon only slightly wider than the distance from New York to Boston, the surface appears geologically inactive. But the ice shell on this moon is unlikely to break as it thins. Thus, Mimas may have had a barren surface with a boiling liquid ocean directly below it. Researchers noticed that the Moon “swings” slightly, which once again confirms the presence of an ocean.
On larger moons, pressure changes are likely to crack the ice surface before the oceans can boil. These larger moons include Titania, which also orbits Uranus. They wrote that the ribbed surface of Titania could have formed during periods of thinning and thickening of the ice shell.
The new publication is not Rudolph's first article about icy moons. An earlier study examined what might happen as icy moons cool and their surfaces thicken. This process can also impact the lunar surface, creating features such as the broken ridges commonly known as “tiger stripes” that can be seen on Enceladus.
What we know about Earth's geology can help us understand how the surface of our planet has changed over millions of years. Studying the icy shifts on these distant moons can also help us understand how their distinctive surfaces formed.
Read more: NASA's Europa Clipper will search for life in the plumes of icy moons
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