A recent study reported that Mimas, a small moon of Saturn that astronomers compare to the Death Star in the “Star Wars” series, contains an ocean of water beneath its icy surface, making it possible to harbor some form of life.
Mimas is part of the family of rare moons in the solar system that contain liquid water under their icy layer. This family includes Jupiter’s moons Europa and Ganymede and Saturn’s moons Enceladus and Titan.
The lead author of the study, which was published in the journal, said:NatureValerie Linney, in a press conference: “If there is one place in the universe where we did not expect to find conditions conducive to life, it is Mimas.”
Linney, an astronomer at the Institute of Celestial Mechanics and Ephemeris Calculus at the Paris PSL Observatory, pointed out that this moon, which was discovered by astronomer William Herschel in 1789, “did not appear to be of much use from its appearance.”
The star, which has a diameter of only 400 kilometers, was called the “Death Moon” because it appeared cold, rigid, and unfit for life. Its surface is full of craters, including a huge crater that gives the false impression that it is similar to the Death Star in the “Star Wars” series.
The moon’s icy crust appeared frozen, with no trace of internal geological activity that might change it, unlike Saturn’s other moon, Enceladus, whose smooth surface is constantly being reshaped thanks to the activity of its internal ocean and its hot springs, which are a source of the heat necessary for the water to remain in a liquid state.
However, the scientists felt that something was happening inside Mimas, according to Lenny. They studied the moon’s rotation around itself and its small oscillations that differed based on the internal structure of the star.
In their first study, published in 2014, scientists were unable to confirm that the moon contains a liquid ocean, and the majority of scientists tended to assume that it contains a rocky core.
“We could have been satisfied with this result, but we were disappointed,” Leni said. The work team used dozens of images taken by the Cassini probe of the US Space Agency (NASA), in order to expand research to include the entire Saturn system and 19 of its moons.
Analysis of the orbital motion of “Mimas”
This data made it possible to analyze the orbital movement of Mimas around Saturn and how it affects its oscillatory movement, and to monitor small differences in this movement, called libration, up to a few hundred metres, which indicates the presence of a liquid ocean under its entire surface.
In an article accompanying the study, Matija Cook of the SETI Research Institute in California and Alyssa Rose Roden of the Southern Research Institute in Colorado said: “This is the only possible conclusion.”
The study reported that the ocean moves under an ice layer whose thickness ranges between 20 and 30 kilometers, a number similar to the thickness of the ocean of the moon Enceladus.
The ocean may have formed under the influence of the gravity of Saturn’s other moons, which are “tidal effects” that shake the star and generate heat that prevents its surroundings from freezing.
Calculations indicate that the ocean was formed only between 5 and 15 million years ago, which explains why no geological signs have been observed on its surface until today.
Nicola Rambo, one of the study’s authors, said that the moon “combines all the conditions necessary to house a form of life: water that remains liquid due to a heat source that contacts the rocks to cause chemical exchanges” necessary for the emergence of a form of life.
Could Mimas harbor primitive life forms such as bacteria or archaea? “Future space missions in the coming decades will have to answer that,” Linney answers.
“One thing is certain: if scientists want to search for the latest conditions favorable to life in the solar system, they must turn to Mimas,” she added.
