Compared to that Star Wars Death Star, Spoileda small Moon of SaturnHouses beneath its icy surface a liquid ocean conducive to the emergence of life, according to a study published by the journal Nature today, February 7, 2024.
Spoiled This means it joins the family of rare moons in the solar system that harbor liquid water beneath their ice shell: Europe And Ganymedearound Jupiter, Enceladus And titaniumaround Saturn.
“If there is a place in the universe where we did not expect favorable conditions for life, that place is Mimas,” explained Valéry Lainey, lead author of the study.
He Satellite of the ringed planetDiscovered in 1789 by astronomer William Herschel, according to this astronomer from the IMCCE (Institute of Celestial Mechanics and Ephemeris Computation) of the Paris Observatory-PSL, it had “not the right appearance at all”.
The celestial body, with a diameter of just 400 kilometers, was nicknamed the “Moon of Death” because it appeared cold, sluggish and therefore uninhabited.
This was because the surface was full of craters, including a huge crater that gave it a similar appearance to the Death Star, the Empire’s station in the Star Wars saga.
Be ice cream bowl It appeared to be frozen, without any trace of internal geological activity that could alter it. On the other hand, the smooth surface of his older sister, Enceladusis regularly transformed thanks to the activity of its internal ocean and its geysers.
However, scientists had a hunch that “something was happening inside.” Spoiledsaid Valery Lainey. They examined the satellite’s rotation around itself and its small oscillations, so-called librations, which can vary depending on the star’s internal structure.
Can Mimas harbor primitive life forms?
His initial work, published in 2014, failed to prove the existence of a liquid ocean. Most scientists tended to believe in the existence of a rock core.
“We could have left it at that, but we were frustrated,” said Valéry Lainey.
His team collected dozens of images captured by NASA’s Cassini spacecraft (2004-2017) to expand their research to the entire Saturn system and 19 of its moons.
This data allowed us to analyze the orbital movement of Mimas around Saturn and how it affects your librations. The discovery of tiny fluctuations in these librations, on the order of hundreds of meters, revealed the presence of a liquid ocean beneath the entire surface.
“It is the only viable conclusion,” stressed Matija Cuk of the SETI Institute for the Search for Extraterrestrial Intelligence (California) and Alyssa Rose Rhoden of the Southwest Research Institute in Boulder, Colorado, in a commentary included in the journal Nature . .
The ocean moves under a 20 to 30 kilometer thick layer of ice, comparable to that of Enceladus, describes the study. It was formed under the influence of the gravity of other moons of Saturn: these are “tidal effects” that shake the star and generate heat, preventing its ocean from freezing.
Calculations indicate that a sea formed recently only between 5 and 15 million yearswhich would explain why no geological signs of its existence have yet been discovered on the surface.
The Moon “fulfills all conditions for habitability: liquid water, maintained by a heat source, in contact with rock, which favors develop chemical exchange“Indispensable for life,” summarized Nicolas Rambaux from IMCCE, one of the authors.
Can Spoiled Host primitive life forms such as bacteria or archaea? “The issue will be addressed in future space missions in the coming decades,” expected Valéry Lainey.
“One thing is certain: if you are looking for the latest habitability conditions in the solar system, you should look for Mimas,” the astronomer concluded.