Scientists are convinced that a vast ocean of salt water lies several dozen kilometers below the icy surface of Europa, making this moon an ideal candidate to host extraterrestrial life in our solar system.

However, it is difficult to determine whether this hidden ocean contains the chemical elements necessary for the appearance of life. Carbon dioxide (CO2), which is, along with liquid water, one of the fundamental building blocks of this process, had already been detected on the surface of Europa, without it being possible to determine its origin.

To find out, two American teams of researchers used data from the James Webb Space Telescope, collected through its infrared observation instrument. They were able to map the surface of Europa, according to two studies published Thursday in the journal Science.

The largest amount of CO2 was found in an area 1,800 kilometers wide, called Tara Regio. This area is covered by "chaotic terrain", consisting of ridges and cracks, according to one of the studies.

It's unclear exactly what creates this jagged terrain, but it could be that relatively warm water from the underlying ocean rises to melt the surface ice, which refreezes over time and forms new bumps.

Table salt

The first study used information from the James Webb telescope to determine whether CO2 could have come from elsewhere, for example from a meteorite.

Conclusion: the carbon "finally comes from the interior, probably from the inner ocean of the moon," Samantha Trumbo, planetary scientist at the American University of Cornell and lead author of the study, told AFP.

In the Taga Regio area, scientists have also detected the equivalent of table salt, making it yellower than the rest of the white plains of Jupiter's moon. An element that could also have emerged from the ocean.

"Now we have CO2, salt: we are starting to know a little more about the internal chemistry" of Europe, says the planetary scientist.

Using the same data from James Webb, the second study also concludes that "carbon comes from within Europe".

Europa, one of Jupiter's three icy moons, is the target of two major space missions that must determine whether its mysterious ocean is suitable for the appearance of life.

"Future missions"

ESA's European space agency's Juice probe was launched last April, and NASA's Europa Clipper is scheduled to fly in October 2024.

They will take eight years to reach Jupiter, the giant of the solar system, and its large moons (Io, Europa, Ganymede and Callisto), discovered by Galileo in 1610.

Olivier Witasse, ESA's Juice project scientist, considers the James Webb telescope's analyses "extremely interesting". "This allows us to learn more about this ocean, located deep under the ice and therefore rather inaccessible in the current state of space exploration," he told AFP.

"This is one of the most fascinating places in the solar system in the search for life outside of Earth," adds the scientist.

When the Juice probe makes two flybys of Europa in 2032, it will collect "a lot of new information," he anticipates. Juice will also inspect Ganymede, which also has a subglacial ocean, and where carbon has been detected.

The Juice and Europa Clipper missions will not be able to directly find extraterrestrial life, but only identify conditions conducive to its appearance. "We leave this challenge to future missions," adds Olivier Witasse. In such an extreme environment, they could only be primitive life forms like bacteria.

© 2023 AFP