Mission looking for life in Europa's water plumes

Later this year, a new chapter in the search for extraterrestrial life begins when NASA’s Europa Clipper space probe sets off for the icy moon of Jupiter that shares its name. It’ll be armed with instruments to confirm whether - as scientists suspect - there might be a vast ocean beneath the surface, and whether plumes of water periodically erupting from the surface contain biological material. Fabian Klenner, at the University of Washington, is one of the scientists testing the tools that will be on the lookout for an historic landmark in space science…

Fabian - Around two decades ago, it turned out that there are moons around Saturn and Jupiter that have liquid water. The water is not on the surface as we know it from earth, but it's on the subsurface under thick ice crusts covering these moons. Life on earth as we know it requires liquid water. We also need enough energy and interesting chemistry, chemical reactions ongoing. And all these ingredients appear to be present on these moons. In particular on Enceladus, a moon of Saturn and Europa, a moon of Jupiter.

Chris - And what keeps the water liquid given it's got that huge thick, icy crust, it's very, very cold there. It's a massive distance away from the sun. We measure the distance in millions of kilometres, don't we? Hundreds of millions of kilometres. So why is it liquid at all?

Fabian - These moons orbit their host planet, not in a perfect circular orbit. At some point they're closer to the planet and sometimes they are not so close to the planet. And these variations and gravitational forces lead to a lot of heat production in the interior of the moons. And this is enough energy to maintain liquid water.

Chris - So they get sort of stretched and squeezed as they go round. If there is life there and it's under hugely thick ice crusts, how can we find it at all?

Fabian - We can send instruments there. There will be the Europa Clipper spacecraft set for launch in October this year, and there will be one instrument on board the spacecraft that's a so-called mass spectrometer that measures ice grains that are ejected from Europa, so that are either knocked off the surface of the moon or maybe even emitted in a geyser. And if there is a mechanism, we don't know that. But if there is life at all, to bring that life into these ice grains, then we have very good chances to use such kinds of instruments to figure out if there is life or not, because the life would be entrapped.

Chris - And the thrust of this project was to ask, well what's the hallmarks of life in those ice grains if it's there?

Fabian - Yes. So we did experiments in the laboratory to simulate what these instruments in space should actually deliver to simulate this process. We used a tiny liquid water beam and injected that into a vacuum, and this liquid water beam disintegrated into droplets. And we prepared this water in a way that we added bacterial cells to our samples so that in theory, one cell is in one of these water droplets. And then we were shooting with a laser onto these water droplets to simulate the process of measuring single ice grains with these mass spectrometers in space.

Chris - What sort of range of types of cells and cell chemistries in organisations can you see? Because we're assuming, of course, that life is going to pop up in these oceans and look very similar to what life does look like on Earth, but that may not be the case at all, mightn't it? So do you think you're geared up in order to detect a range of different forms of life, regardless of what it looks like?

Fabian - So I always like to argue that there is plenty of liquid water on these moons. There is plenty of energy, there is organic chemistry, so the same ingredients are there. And I personally think it is not a bad approach to look for life as we know it on an ocean moon, like Enceladus or Europa. And so this is why we were focusing on bacterial cells that we know from Earth. And we were particularly looking at cell culture that likes cold environments that are very small, so that could fit into these ice grains. And also the same culture likes only low nutrient fluxes.

Chris - A good friend of mine, John Zarnecki, built the Huygens lander or helped to build the Huygens lander that landed on Titan, Saturn's largest moon. And I remember him saying, this will take seven years to get from launch to there. And he said, it's a long time to wait to find out whether or not you've succeeded. How long are you going to have to wait?

Fabian - <laugh>? I probably have to wait about six years, maybe six and a half. So Europe Clipper should arrive in the Jupiter system in 2030, and then hopefully return data very, very soon.

Chris - And hopefully you've got some other projects to work on in the meantime. Otherwise, you could be a very, very quiet scientist for the next six years.

Fabian - I definitely won't be very quiet. There's plenty of work to do and plenty of things to prepare for Europa Clipper and also other hopefully upcoming missions.