Cracks in Europa would hide pockets of water where extraterrestrial life is possible

De nombreuses fissures craquèlent la surface d'Europe, l'un des quatre grands satellites de Jupiter © Nasa, JPL-Caltech, Seti Institute

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Of Jupiter’s four largest moons, Europa is the most likely to harbor extraterrestrial life. With its gigantic ocean of salt water covered in ice that would contain two to three times more water than the Earth, this icy Jovian moon harbors many secrets that researchers are trying to unlock.

In a study published on April 19, 2022 in the journal NatureCommunications, researchers have drawn a parallel with a phenomenon… from Greenland! They show there that the layer of ice which surmounts theeuropean ocean could be a real dynamic system allowing exchanges with the outside. A potential chance to harbor life, therefore.

Its ice shell would promote exchanges with the outside

Europe might as well have a lot in common with northwest Greenland. Specifically, with a characteristic formation nicknamed “double-ridge”, captured by a team of geologists from Stanford University. In their study, the researchers draw a parallel between this double ridge and the europe ice structure.

“We were working on something totally different related to the climate change and its impact on the surface of Greenland when we saw these tiny double ridges — and we could see the ridges go from ‘unformed’ to ‘formed'”said Dustin Schroeder, Associate Professor in Geophysics at Stanford University and co-author of the study.

Probed in detail with ice-penetrating radar, scientists found pockets of shallow liquid water just below these ridges, much closer to the surface than the ocean below the ice. A proximity that would allow much more exchanges with the outside world. “Because they are near the surface, where there are chemical elements from space, other moons and volcanoes of Io, there is a possibility that life might have a chance inside the water pockets of the shellexplains Dustin Schroeder, professor of geophysics at Stanford University and co-author of the study. If the mechanism we see in Greenland is similar to how these things happen on Europa, that suggests there is water everywhere.”

Countless cracks for as many life chances

Appearing to split the icy moon in all directions, the double ridges of Europa’s surface can reach a height of more than 300 meters, separated by valleys of more than a kilometer. First observed in the 1990s by the Galileo probe which signed its clap of end in 2003, the researchers had since not found a definitive explanation on their origin. Today, it is thanks to this analogy with the double ridges of Greenland that an answer has been found, as the authors of the study recall: “The mechanism we propose in this paper would have been almost too bold and complicated to propose without seeing it happen in Greenland”said D. Schroeder.

This typical structure would have been created by a phase change of the water contained in the pockets located just below the first layer of ice: the liquid water rises to the surface through the cracks in the ice, then solidifies once lifted. Over time, it accumulates in one place, creating a ridge.

“In Greenland, this double ridge has formed where water from surface lakes and streams frequently flows to the surface and freezes again.said Riley Culberg, first author of the study and doctoral student at Stanford. One way similar shallow pockets of water could form on Europa would be for water from the subterranean ocean to creep into the ice shell through fractures — and this would suggest there might be a reasonable amount exchanges inside the ice shell.

An increasingly probable habitability

The researchers point out that their model is only“another hypothesis in addition to many”except that they have “the advantage that our hypothesis has observations of the formation of a similar feature on Earth to back it upas R.Culberg explains. It opens up all these new possibilities for a very exciting discovery.”

Because even if this satellite of Jupiter is located outside the habitable zoneit is he who has the highest probability of harboring life, according to scientists, with the moon Enceladus (around Saturn). This last discovery increases the probability, thanks to the possible exchanges of nutrients with the surface.

Many missions intend to confirm or invalidate this hypothesis of life on Europa, such as Europa Landerdeveloped by ESA, and Europa Clipperof the Nasa. For the latter, a radar similar to those used to study the ice caps is planned, which will make it possible to check the presence — or not — of pockets of water under the double ridges.

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