Exobiology: oxygen in the ocean of Europa, the moon of Jupiter?

At a time when the search for life elsewhere than on Earth will enter a new phase with the James Webb telescopeit is worth recalling that in the early 1980s, in his famous novel 2010: Odyssey twoArthur Clarke — the famous inventor of the concept of geostationary satellite — was already taking seriously the idea that life forms could possibly exist in the ocean under the pack ice of Europe, the moon frozen from Jupiter.

He was only partly taking over for his hard SF novel the results that we had just obtained after the success of the missions Travel 1 and 2 during their visits to the moons of Jupiter. As Futura has explained in previous articles, the discovery of the Io volcanism had been made and the first close-up images of the European sea ice had been obtained.

Inspired by those of life forms in the vicinity of hydrothermal springs in the abyss during the 1970s, some had speculated that there might be similar ones in the ocean of Europe, with a volcanism from, as in the case of Iofrom tidal forces of the Jupiterian system. This is perhaps how life on Earth was born, in the walls of fireplaces of hydrothermal springs similar during theHadean or at the beginning of theArchean.

These ideas have only gained more and more weight over the years, to the point that missions to Europe, directly or indirectly, have been considered or are already in preparation such as Juice and especially Europa Clipper.

Non-biogenic oxygen over Europa

Let us recall that on our Blue Planet, the hydrothermal vents discovered in the oceans since the 1970s in the vicinity of volcanically active zones are oases of life drawing their energy of the chemosynthesis made of sulfurwithout the light from Sun. There are good reasons to believe that the use ofoxygen by living forms was an evolutionary milestone because it provides a much more efficient source of energy.

This oxygen is mainly produced on Earth by photosynthesis and it is therefore hard to see how this could happen in the global ocean under the pack ice of Europe, which is already very far from the Sun anyway. One could therefore think that this is a limiting factor towards the evolution of complex life forms on Europa. Indeed, some wonder if the famous cambrian explosion on Earth was not favored by more oxygen available.

However, a group of planetary researchers led by members of theUniversity of Texas in Austin (USA) advances in an article published in Geophysical Research Lettersand of which a summarized version is in free accessthat the ocean of Europe could be as rich in oxygen as the oceans of the Earth.

The idea is not actually new, but it is supported here by numerical simulations taking into account the impact of the large flux of charged particles bombarding the icy surface of Europa, a flux so large that it is known to make it difficult for a fairly limited time, even with hardening of the electronics, the operation of a probe orbit closer around Europe.

the physical model implemented focuses on the behavior of sea ice salt ice at the level of analogues of so-called chaos landscapes in geomorphology on Earth. In the case of Europe, these are landscapes made up of fissures, ridges and blocks of ice that cover a quarter of the frozen world.

A priori, the oxygen generated by the dissociation of water molecules from the ice under the action of photons filters not filtered by a atmosphereas is the case on Earth, and especially under the action of charged particles, very energetic in the magnetosphere close to Jupiter, should not be able to diffuse through the at least 10 km thick pack ice covering Europe.

However, there are reasons to think that at the level of chaotic terrains, there is brine connecting the surface of Europa to its interior. Numerical simulations suggest that this fluid could take on oxygen and diffuse, percolate through the fractures of the pack ice under these terrains, eventually reaching the internal ocean.

However, there is a large uncertainty about the resulting oxygen supply, by a factor of 10,000 in fact, even if the calculations also suggest that around 86% of the oxygen produced on the surface should reach the interior of ‘Europe.

We may know more once the launch of the probe Europa Clipper carried out hopefully in 2024. But it will have to wait for its arrival around Jupiter in 2030 for the studies to begin.