In 1789, astronomer William Herschel discovered two moons of Saturn: Enceladus and the one who was later called one of the giants of Greek mythology: Spoiled. The ones from the Cassini probe On these icy moons they were able to discover that Enceladus hides an ocean of thermal vents, the products of which are ejected into space through huge clouds of ice and gas.
However, Mimas reminds some the Death Star from Star Wars, presents a surface full of craters that doesn’t reveal that such a thing exists large body of water It’s cold down below, but that’s exactly what a team of French researchers discovered by reviewing data taken by the Cassini spacecraft before its spectacular disintegration in Saturn’s atmosphere in 2017.
Although some previous studies have already suggested this, says the new article published this week by the journal NatureThe subterranean ocean of Mimas is relatively new and still evolving.
Under a frozen layer of 20-30 km
The simulations suggest that it appeared a long time ago between 25 and 2 million years, and that lies under a layer of ice about 20 to 30 km deep. The ocean-ice interface reached this depth relatively recently, less than 2 or 3 million years ago, so it would not have had time to leave its mark on the lunar surface.
To reach these results, the researchers examined data from this satellite’s orbit. “We used tens of thousands of images of Saturn’s 19 moons to fully constrain the orbital dynamics of the entire system,” the lead author tells SINC. Valery Laineyfrom the Paris Observatory, “and later we were able to determine the orbital motion of Mimas so precisely that we could detect a slight change in the drift of the orientation of this orbit in space.”
Previous research had suggested two possibilities to explain what the interior of Mimas looks like: a solid body with a rocky core elongated or with a global ocean beneath its surface. Lainey and his colleagues’ analysis revealed changes in the small moon’s rotational motion and orbit that are influenced by its interior.
Applying the solid model would require the rock core to be elongated and almost pancake-shaped, which is inconsistent with orbital observations. Instead, measurements of Mimas’ position suggest that the evolution of its orbit is best explained by the influence of an internal ocean.
Lainey recalls that there are already four moons with a global ocean: “Europe, Ganymede (both from Jupiter), Titan and Enceladus (from Saturn), and now Mimas is added, plus a few other candidates like Callisto, Dione and Triton .” ”
There have been four moons with a global ocean: Europa, Ganymede, Titan and Enceladus, and now Mimas is added, plus some other candidates such as Callisto, Dione and Triton
Mimas (center) joins the “club” of moons with a global ocean: Enceladus and Titan (left) and Europa and Ganymede (right). / Frédéric Durillon, Animea Studio/Observatoire de Paris – PSL, IMCCE
The researcher clarifies that the technique they use requires very precise data on the movement of objects and may not be applicable to other satellites: “It works better for objects close to their planet. In practice, it will probably not be possible to apply it.” This method will be rolled out to many other moons until data from future space missions becomes available.
In any case, these results suggest that recent processes on Mimas may have been common in the early stages of the formation of other icy worlds, according to the authors, who believe that new studies of this moon of Saturn could tell us more about the formation of the frozen worlds
In a parallel review, also published in NatureAmerican astronomers Matija Cuk alreadyLyssa Rose Rhoden conclude: “The findings of Lainey and his colleagues will stimulate a comprehensive study of medium-sized icy moons across the solar system and force a rethinking of what constitutes an oceanic moon.”
Reference:
V. Lainey et al. “A recently formed ocean inside Saturn’s moon Mimas.” Nature