CAPE CANAVERAL, Fla. Astronomers have uncovered compelling evidence suggesting the presence of a vast, youthful ocean beneath the icy shell of Saturn’s Death Star-like miniature moon.
In a study published Wednesday in the journal Nature, a team led by French researchers revealed their analysis of Mimas’ orbit and rotation. Their findings strongly support the existence of an ocean lying 12 to 18 miles (20 to 30 kilometers) beneath the moon’s frozen exterior, rather than a elongated rocky core.
The research, based on data collected by NASA’s Cassini spacecraft, marks a significant milestone in our understanding of the solar system’s moons. Cassini meticulously observed Saturn and its myriad moons for over a decade before its mission-ending plunge into the gas giant’s atmosphere in 2017.
Despite its modest size—barely 250 miles (400 kilometers) in diameter—Mimas lacks the characteristic fractures and geysers typically associated with subsurface activity on moons like Saturn’s Enceladus and Jupiter’s Europa.
“Mimas was probably the most unlikely place to look for a global ocean — and liquid water more generally,” remarked co-author Valery Lainey of the Paris Observatory in an email statement. “So that looks like a potential habitable world. But nobody knows how much time is needed for life to arise.”
According to Lainey, the ocean likely occupies about half of Mimas’ volume, yet given the moon’s diminutive size, it represents only 1.2% to 1.4% of Earth’s oceans. Despite its small stature, Mimas boasts the second-largest impact crater of any moon in the solar system, earning it the comparison to the fictional Death Star space station from “Star Wars.”
“The idea that relatively small, icy moons can harbor young oceans is inspiring,” commented Matija Cuk from the SETI Institute and Alyssa Rose Rhoden from the Southwest Research Institute in an editorial accompanying the study. They were not involved in the research.
The estimated age of Mimas’ subterranean ocean falls between 5 million and 15 million years, rendering it too young to have left discernible marks on the moon’s surface. Lainey suggested that while the overall temperature of the ocean hovers around freezing, the water at the ocean floor could be significantly warmer.
Co-author Nick Cooper from Queen Mary University of London noted that the presence of a “remarkably young” ocean of liquid water positions Mimas as a prime candidate for investigating the origins of life.
Discovered in 1789 by English astronomer William Herschel, Mimas derives its name from a giant in Greek mythology.
Gary P Hernal started college at UP Diliman and received his BA in Economics from San Sebastian College, Manila, and Masters in Information Systems Management from Keller Graduate School of Management of DeVry University in Oak Brook, IL. He has 25 years of copy editing and management experience at Thomson West, a subsidiary of Thomson Reuters.
