Saturn’s icy moon Mimas may be a “hidden” ocean world, according to new research.
Mimassmallest and innermost Saturn‘s large moons are believed to generate enough heat to support a subsurface ocean of liquid water. Recent simulations of the moon’s Herschel impact basin—the most prominent feature on its heavily cratered surface—support the absence of tectonics on Mimas, as well as the existence of a geologically young interior ocean surrounded by a thinning ice crust. statement (opens in new tab) from the Southwest Research Institute (SwRI) in San Antonio, Texas.
“In the waning days of NASA Cassini During the Saturn mission, the spacecraft detected an interesting libration, or oscillation, in the rotation of Mimas, which often indicates a geologically active body that can support an internal ocean,” said Alyssa Rhoden, co-author of the new study and a scientist at SwRI, in a statement.
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But despite this wobble, Mimas’ heavily cratered surface initially led scientists to consider the moon a frozen block of ice. This is because most oceanic worlds – such as geysers erupt Enceladus, one of Saturn’s other moons—is prone to fracture and shows other signs of geological activity. However, Mimas has no defining tectonic features.
“Mimas, marked by a giant impact crater with an icy, heavily cratered surface that closely resembles a small moon, seemed an unlikely candidate. The Death Star “From Star Wars,” Rhoden said in a statement. “If Mimas has an ocean, it represents a new class of small, ‘stealth’ ocean worlds with surfaces that don’t betray the presence of an ocean.”
When modeling the formation of Herschel basin of influence, scientists determined that Mima’s ice cap must have been at least 34 miles (55 kilometers) thick at the time of impact. Meanwhile, observations of Mimas and models of its internal heating suggest its current ice sheet is less than 19 miles (30 km) thick, according to the release.
These measurements show that the interior ocean has warmed and expanded since the basin formed. Moreover, the researchers were only able to recreate the shape of the basin when they only included the interior ocean in their models.
“We found that Herschel could not have formed in an ice crust of its current thickness without destroying the ice crust at the impact site,” Adeene Denton, the study’s lead author and a postdoctoral researcher at the University of Arizona, said in a statement. “If Mimas has an ocean today, the ice sheet has been thinning since the formation of Herschel, which may explain the lack of rifts on Mimas. If Mimas is a developing ocean world, this places significant constraints on the formation, evolution, and habitability of all medium-sized Moons of Saturn.”
These new models challenge scientists’ current understanding of thermal-orbital evolution, Rhoden said in a statement.
“Assessing Mimas’ status as an oceanic moon will compare models of its formation and evolution,” Rhoden said. “It will help us understand better Saturn’s rings and medium-sized moons, as well as the proliferation of potentially habitable ocean moons, especially on Uranus. Mimas is an attractive target for ongoing research.”
These were their findings Posted on December 26, 2022 (opens in new tab)In Geophysical Research Letters.
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