As the Cassini spacecraft continues to circle its target, scientists on both sides of the Atlantic are already contemplating their next mission to Saturn. However, this time the subject of interest of scientists is not the gas giant itself. They are going to seek life … in the rings of Saturn.
Two Saturian moons - Titan, the world of frozen methane seas, and a frozen ball hiding the ocean in its depths, Enceladus - were on the "short list" of places in the solar system where extraterrestrial life could presumably exist. And scientists are determined to find out for sure. This became clear at the American Geophysical Union Conference last week, where American and European researchers presented their proposals for two of the most promising spacecraft that could determine if two of Saturn's most mysterious moons are inhabited.
The American side presented the Enceladus Life Finder (ELF), a new class of research spacecraft proposed by NASA, the essence of the task of which lies in its very name. The goal of the ELF is "simple": it will descend to a height of 50 kilometers above the south pole of Enceladus, where the existing cracks in the satellite's ice crust spit out into space the instantly freezing water of the subglacial ocean.
By diving into the geysers of the south pole of Enceladus, ELF will be able to collect samples of the satellite's ocean water, as the Cassini orbiter has already done, but with the help of more suitable and modern instruments. Two state-of-the-art mass spectrometers will look for key signatures of life as well as traces of hydrogen gas (the energy source). In addition, the spacecraft will directly search for life by measuring the composition of amino acids and carbon isotopes, which appear in special conditions in the presence of microorganisms.
Enceladus structure
“It is a very high hope for us that ELF will be able to characterize the level of habitability of the Enceladus ocean,” says Linda Spilker, one of the Cassini project contributors and supporter of the ELF idea.
"I'd love to know if Enceladus can sustain life, or better yet, find evidence of this life."
Promotional video:
From all that we know at the moment, the subsurface ocean of Enceladus may be the place closest to terrestrial conditions.
However, there is a possibility that there is a place with a completely different form of biology, so incredible that assumptions about it simply cannot fail to make us see it for ourselves. And now we are talking about the methane seas of Titan. So why should the search for extraterrestrial life be limited to only one place, if you can "kill two birds with one stone" at a time?
This task will be assigned to the apparatus "Explorer of Enceladus and Titan" (Enceladus and Titan Explorer), or E2T for short, proposed by the European Space Agency. Similar to the ELF device, the E2T device will be able to fly over the south pole of Enceladus (but only six times) at an altitude of 50 to 150 kilometers and with the help of two mass spectrometers will study the water for signs of life. In addition, E2T will be equipped with a state-of-the-art space camera that will be able to capture images of the surface of Enceladus in very high resolution (at a scale of one meter of surface per pixel).
Hypothetical model of a methane-based cellular organism living in the oceans of Titan
After completing the mission with Ecelad, the E2T will travel to cloudy Titan, where it will collect and analyze samples as part of 17 flights through the satellite's atmosphere at altitudes ranging from 1,500 to 900 kilometers above the surface. We already know that there is some "prebiotic chemistry" in the sky of Titan - organic reactions that could lead to the formation of RNA and proteins. With E2T, we can see how close this chemistry has gotten to creating the building blocks of life.
The E2T probe will also take detailed images of Titan's surface, featuring terrestrial rivers and canyons covered in liquid hydrocarbons instead of water.
Giuseppe Mitri, the main proponent of the E2T idea, believes it is time for an astrobiological mission to the outer reaches of the solar system.
"This idea is attracting a lot of public attention," says Mitri, adding that the interest was even higher than in the case of the new ExoMars mission, which also aims to find traces of extraterrestrial life.
Now, of course, no one would argue that one of these space missions will receive the green light. And even if they ultimately received support, it will take more than one year before the actual implementation of these projects. The ELF project wants to receive the allocated funds by 2025, with an expected arrival to Saturn by 2030. In turn, the E2T spacecraft, in any case, will not leave home before 2030 (and this is with the most optimistic forecasts).
Both proposals require investments of hundreds of millions of dollars for implementation, so both have to compete in the desire to attract the necessary funds not only among themselves, but also with many no less interesting ideas. A potential mission to explore Venus, a close encounter with one of the Trojan asteroids, and the collection of soil samples from the surface of the moon's south pole. Sounds incredibly tempting, right? But this is far from all that modern scientists offer.
And yet, if fresh thoughts of the astrobiological community attract the attention of the necessary funds, then within a decade or two we can return to Saturn. And when we get there, the main task will be to find life. Maybe it's really enough to search for stones and dig in the sand? Maybe it's really time to get to know your neighbors?
NIKOLAY KHIZHNYAK