Europa is a prime candidate for the search for extraterrestrial life in the solar system due to the supposed presence of an ocean of liquid water. But this ocean would be located under a thick layer of ice, up to 20 or 30 kilometers below the surface, according to data collected by space probes.
However, part of this water could be much closer to the surface than we imagine, according to the study published Tuesday in NatureCommunicationswhich emphasizes that Europe is
young and geologically active.
The most widespread geological structure consists of double ridges, a kind of furrow that can stretch for hundreds of kilometers and whose edges can rise up to several hundred meters.
Scientists have put forward several hypotheses to explain their formation, including an interaction between the inner ocean and the layer of ice that covers it. However, the difficulty of water passing through such a thick surface has led to speculation that ridge formation occurs with pockets of water located just below the surface.
This is precisely what a team of geophysicists from the American University of Stanford was able to observe… in Greenland, an island mainly covered in ice.
They discovered there
a double ridge of ice that is similar in shape to the double ridges found on Europa, explained to AFP Riley Culberg, doctoral student in electrical engineering at Stanford and main author of this study. This double ridge is about 800 meters long with an average height of 2.1 meters and is located about 60 km from the coast in northwest Greenland.
His colleague Dustin Schroeder, professor of geophysics at Stanford, explains that they were
working on something completely different related to climate change and its impact on the surface of Greenland when [ils ont] saw those little double ridges.
Satellite images and data collected by airborne radar allowed
for the first time to see something similar ([à Europe] on Earth and to observe the subsurface processes that led to the formation of the ridgesexplained Riley Culberg.
The team modeled a process that involves freezing, pressurizing and fracturing a shallow pocket of water, all leading to the formation of the double ridge.
The water we observed in Greenland is in the top thirty meters of the ice sheet, says Culberg. On Europa, whose crests are much higher and longer, he estimates that
the water pockets could form between one and five kilometers deep.
If their mechanism of formation is indeed the one proposed, these pockets could be very widespread. And if the water that composes them comes from the internal ocean, they could contain traces of extraterrestrial life.
Two future space missions will provide more information from 2030. Europa Clipper, for NASA, will be equipped with a radar similar to that used to study Greenland. JUICE, for the European Space Agency (ESA), will also look at Europa as well as Jupiter’s two other icy moons, Io and Ganymede.