If we look at our own Greenland, Europe – one of the best candidates for extraterrestrial life in our solar system – may be much more attractive for life than we think.

When it comes to habitability, Jupiter’s moon Europa is already in very good shape; studies have shown that the moon has one of the most important ingredients for life as we know it: liquid water. In fact, the moon would have a worldwide ocean (filled with salt water). However, we must add an important caveat: the ocean is hidden under an ice sheet that is kilometers and in some places even tens of kilometers thick. Obviously, it makes it difficult to sample that ocean and determine whether it really has as much potential from an astrobiology point of view as we now think. To get some idea of ​​what is happening under the ice sheet, researchers can do little more than study the surface of that ice sheet in detail and hope that certain properties give away more. And that is exactly what scientists have now done. And the study tentatively hints that Europe may be an even better candidate for extraterrestrial life than we dared to hope.

Double Ridges

In their research – published in the magazine Nature Communications – the researchers focus on the double ridges with which Europe is richly scattered. And they argue that, based on a similar phenomenon we know from our own Greenland, these may hint at the presence of water reservoirs relatively close to the surface of the ice sheet.

Chemicals

If these superficial water reservoirs are indeed hidden under those double ridges on Europe, that is good news for several reasons, says researcher Dustin Schroeder. “Liquid water near the surface is a very tantalizing and promising place, where you can imagine life has a chance.” Not least because of the interaction with the surrounding space. “Because it’s closer to the surface, you have more interesting chemicals there from space, from other moons and the volcanoes of Io.”

The research

The idea that liquid water could be found not only deep under the ice sheet of Europe, but also inside that ice sheet – even fairly close to the surface – arose more or less by accident, says Schroeder. “We were working on something completely different related to climate change and the impact it is having on the surface of Greenland when all of a sudden we saw those little twin ridges; and we were even able to see how they (on Greenland, ed.) originated.” Further research – in which the scientists make use of radar measurements – subsequently revealed how these ridges were formed. “In Greenland, these double ridges form at places where water from surface lakes and streams (via fractures, ed.) sinks into the ice sheet and freezes again,” said researcher Riley Culberg (see also the video below).

And similar ridges are thus found on the surface of Europe. “One way that similar surface water reservoirs can form on Europa is because water is pushed up from that subsurface ocean through fractures in the ice sheet,” Culberg explains.

Water everywhere?

As mentioned, these fairly superficial water reservoirs should be able to incorporate chemicals from the surrounding space quite easily. In addition, they should of course also be a lot easier to sample than the much deeper ocean from which the water they are filled comes from. Finally, judging by the double ridges that we see in Europe, they may also be very numerous. “If the mechanism we see in Greenland is also the one in Europe, then it suggests that there is water everywhere,” Schroeder said.

With the research, the evidence continues to pile up that Europe’s thick ice sheet is not an impenetrable barrier. Previously, water plumes escaping Europe’s ice sheet already indicated that ocean water knows how to make its way through that ice sheet and that the ocean is therefore not completely isolated from the outside world. And this study also hints that the ice sheet is quite dynamic, in the sense that it facilitates contact between the ocean beneath the ice sheet and the chemicals deposited by nearby celestial bodies on the ice sheet. And with that, the idea that life can arise and survive under the ice sheet seems to be becoming increasingly plausible.

Whether life can actually be found under the ice sheet of Europe remains shrouded in mystery even after this study. It is hoped that future missions to the moon can provide more insight into this. Fortunately, those missions are now in the pipeline; NASA hopes to launch the Europa Clipper in 2024. Also on board this probe is a radar specifically designed to reveal the structure of the ice sheet. And ESA is currently working on JUICE: a probe to be launched in 2023 and to study some of its moons, including Europa, in addition to Jupiter.