Evidence of a deep global ocean beneath the crust of Saturn's moon Mimas (sometimes called the “Death Star”) has puzzled astronomers because it's so impossible to find one.
A new analysis of observations from the Cassini spacecraft, which explored Saturn between 2004 and 2017, indicates that Mimas has a rolling motion (a phenomenon known to astronomers) as it orbits. liberation) is caused by a liquid ocean beneath its surface, rather than a completely solid core.
The new discovery adds to the number of verified underground oceans in our solar system. It also raises the possibility that life may have evolved there.
“It was a big surprise,” says the astronomer and lead author of the new study Valerie LaineyIt studies the dynamics of Saturn's moons at the Paris Observatory (France).
Mimas has been christened the “Death Star” because a giant impact crater on one side gives it the appearance of the famous space station. Star Wars; On Earth, a crater of comparable size would be wider than Canada. Mimas, one of the many moons around Saturn (146 at last count), rocks strongly from side to side during its orbit around the planet.
This release can be explained in two ways: Mimas had a very elongated core, like a flattened rugby ball; Or there was a universal ocean beneath its surface.
Lainey was part of the team that first proposed in a 2014 paper that Mimas might have a hidden ocean. Science.
But the idea has largely been dismissed because there are no signs of such an object on its surface, unlike Saturn's other moon Enceladus, which sprays water from its interior ocean into space.
The researchers suggest that the oceans do not freeze due to heat from tidal forces when the moon orbits Saturn.
Plus, it's a significant body of water: Mimosa is relatively small, but its underground ocean makes up half its mass, Lainey says.
“Now a lot of people look at this and say, 'Oh my god, there really is a global ocean,'” Lainey says.
So far, astronomers have only found clear signs of subsurface oceans in two of Saturn's moons (Enceladus and Titan) and Jupiter's moons (Europa and Ganymede).
As previous studies have noted, life is most likely to exist where liquid water exists, so subterranean oceans are ideal places to look for extraterrestrial life, which scientists speculate may have formed around hydrothermal vents in the cores of moons.
Recent research suggests that the Mimas Ocean must be young: 2 to 25 million years old, almost no time in celestial terms.
The time that life evolved there may seem very short.
But Lainey says the Mimas Ocean, relatively warm and rich in chemical raw materials, would be an ideal place for life to evolve.
He admits, however, that drilling down there is difficult: Although the Mimas Ocean appears to be very deep (more than 40 miles deep in some places), its top is up to 18 miles beneath the rock's outer crust. Ice cube.
Mimas may also help scientists understand how other alien oceans developed.
The moon is slightly smaller than Enceladus and is made of the same types of rock and ice, Lainey says, indicating that their chemistry and geology are similar.
However, Enceladus' surface ocean is about a billion years old, while Mimas is much younger, perhaps providing scientists with a window into Enceladus' early development.
A giant impact crater that makes Mimas look like the Death Star is a sign that its ocean must be relatively young, says planetary scientist Alyssa Rose Rhoden of the Southwest Research Institute in Boulder, US.
Crater (named after the astronomer Herschel William Herschel(discovered by Mimas in 1789) formed hundreds of millions of years ago when an object several kilometers in diameter collided with the Moon.
Rhoden was not involved in the latest study, but is a co-author In the article Nature He says that the Herschel impact would have pierced the crust of Mimas if there had been a subsurface ocean; So, what Herschel looks like means there was no sea at that time.
The discovery reinforces the idea that underground oceans may exist elsewhere in our solar system, particularly on many of Uranus' moons and even on some of the planet's material. The Kuiper BeltIt orbits the Sun beyond Pluto.
“It's a little weird, but yes: after all, you can expect liquid water in many things,” says Lainey; “Even Mimas, the most unlikely place in the solar system, has a universal ocean.”
