Teresa Guerrero Madrid

Madrid

Updated Wednesday, February 7, 2024-17:00

Another moon in our solar system joins the small list of icy worlds that scientists believe host an underground ocean, expanding the catalog of satellites in which to investigate whether they potentially meet the conditions to be habitable and how it arises. life.

This is Mimas, one of Saturn's moons. A French team has found evidence that suggests that this satellite discovered in 1789 by William Hershchel has an ocean beneath its icy surface sculpted by craters, as argued this Wednesday in the journal

Nature

.

It would be a relatively recent ocean (on geological scales) and still evolving.

The research has been carried out with data collected by NASA's Cassini spacecraft. It was launched into space in 1997 and was examining Saturn and its family of icy moons for a decade, until its mission ended in spectacular fashion in 2017, penetrating the atmosphere of the ringed planet at 113,000 kilometers per hour to self-destruct. The wealth of data he collected continues to be analyzed by scientists, as this new study shows.

There is increasing evidence that some moons may have oceans beneath their surface, but detecting these aquatic worlds is a challenge for scientists because at the moment, with current technology it is not possible to take samples of these oceans and obtain direct evidence. .

Mimas

was, in principle, a candidate with little probability of hosting a mass of water,

since its cratered surface is different from other moons with oceans such as Enceladus (a moon of Saturn in which phosphorus and other chemical elements considered necessary for a place is habitable) and Europa (a satellite of Jupiter with geysers). Both are considered the most promising places to host life outside of Earth and are therefore the reference moons in this type of studies on the Solar System.

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Over the last few years and thanks to spacecraft such as Voyager and Galileo, scientists have found evidence that suggests that Europa's ocean resembles that of Earth and may be habitable. They also believe that the oceans of the moon Ganymede (of Jupiter) or Titan (another satellite of Saturn), may have been formed by similar processes.

However, Valery Lainey of the Sorbonne University in Paris and his colleagues challenged the hypothesis that Mimas was different and investigated the possibilities that it had an ocean, using observations made by the Cassini spacecraft for their study.

Two theories about the interior of Mimas

Previous research had suggested two possibilities for the interior of Mimas: that it had an elongated rock core or a global ocean. Many scientists opted for the first option, that of the rocky core. However, the latest analyzes by Lainey's team have shown that changes in the moon's rotation are affected by the interior composition. As explained in the article,

the evolution they have observed in its rotation is better explained if the interior of the moon is an ocean.

According to their estimates, this large mass of water would be found under a layer of ice between 20 and 30 kilometers deep. Through models and simulations, they have also calculated that

the ocean would have emerged between two and 25 million years ago

, so in geological terms it would be young and there would not have been time for that ocean to leave marks on the surface of the moon.

And the idea that Mimas has an ocean and that it could have formed recently has implications for the knowledge that until now existed about its geological characteristics. Thus, they believe that the large 139-kilometer crater on its surface, called Herschel in honor of the discoverer of Mimas, could have formed in an icy crust that was not as thin as previously thought, but several tens of kilometers deep. The appearance that this crater gives it, by the way, has caused this moon to be compared to the fictional Death Star, the imperial space station from

Star Wars.

The moon Mimas

"The idea that relatively small, icy moons could harbor young oceans is inspiring, as is the possibility that transformative processes have taken place in the more recent history of these moons," note Matija Cuk (SETI Institute) and Alyssa Rose. Rhoden (from the Southwest Research Institute in Boulder, USA), in an article also published today in

Nature

in which the research on Mimas is discussed.

These two researchers consider that "the fact that Mimas has been added to the catalog of worlds with oceans changes the general picture" that until now had about the appearance that these celestial bodies had to have and "opens

the door to examine other moons medium-sized in the Solar System

." As an example, they mention a series of medium-sized icy moons that orbit Uranus and that are going to be the main objective of a NASA mission.

A 'lesson' for scientists

"Mimas has taught scientists a lesson: intuition is excellent for generating hypotheses, but it is not enough for drawing conclusions. The Solar System will always give us surprises, and

researchers must be open to new ideas and unexpected possibilities to recognize them" Cuk

and

Rose point out.

In the coming years, they will have new data to continue investigating the habitability of these moons because there is great interest in space agencies to study these worlds in

situ

. One of the most ambitious European missions, JUICE took off last April and is heading to the Jupiter system to explore Ganymede, Europa and Callisto, and find out if the oceans of liquid water that these icy moons are believed to have have the necessary ingredients. for life to emerge.

The JUICE spacecraft is scheduled to reach its destination in 2031 and, in the meantime, future missions are already being planned. In fact, investigating the moons of the giant planets of the Solar System is one of the three main scientific priorities that the European Space Agency (ESA) established in its Voyage 2050 strategy, which includes the objectives for the period 2035-2050 (the other two priorities are the study of exoplanets and the study of the early stages of the Universe). For ESA, "

investigating the habitability potential of worlds in our Solar System is essential to understanding the emergence of life

and is of particular relevance in the search for Earth-like planets beyond our Solar System." And although 2035-2050 may seem like a long-term plan, space missions require years of preparation from the time they are conceived and proposed by scientists, and approved, until they fly into space.