Ice grains ejected from alien moons could bear signs of life

The Oceans some of which lie under a thick layer of ice Moons of Jupiter and Saturn are the main candidates in the search for Life Extraterrestrial.

This is shown by a new study from the University of Washington in Seattle (UW, USA) and the Free University of Berlin (Germany). Ice grains The material ejected from these planetary bodies may contain enough material for instruments launched in the fall to detect signs of life, if present. The study is published in the open access journal Scientific advances.

“For the first time, we have shown that even a small fraction of cellular material can be identified using a mass spectrometer on board a spacecraft,” emphasizes the lead author. Fabian Klenner from the UW, “Results that give us more confidence that the new instruments can detect life forms similar to those on Earth that we are increasingly convinced may exist on moons with oceans.”

Particularly in at least two of these frozen worlds. One is the moon Enceladus Saturn, where the Cassini mission that ended in 2017 discovered parallel cracks near its south pole. Plumes or plumes containing gas and ice grains emerge from these cracks.

Illustration of the interior of Saturn’s moon Enceladus, which hides a subsurface ocean of hot springs, the products of which rise through its icy crust and are ejected into space by giant clouds or clouds of ice and gas in the southern region. / NASA/JPL Caltech

On the other hand, there is the icy moon Europe of Jupiter. Another article was also published in the same week Scientific advances where its ice layer is found to be at least 20 kilometers thick. She will be leading the mission Europe Clipper from NASA, launch is scheduled for October.

To prepare for this mission, researchers are studying what they do new generation of instruments, which will analyze Europe in detail. It is not technically possible to directly simulate how ice grains fly through space at a speed of 4 to 6 kilometers per second – as happens in reality – and collide with these observation devices.

Experiment in the laboratory

Instead, the authors used a Experimental setup that sends in thin stream of liquid water into a vacuum, where it breaks up into droplets. “For our laboratory experiments, we simulate the ice grains of Europa or Enceladus (where they have a diameter between one and five micrometers) using these liquid water droplets with a diameter of 15 micrometers,” Klenner explains to SINC.

Next, they used a laser beam to excite the droplets and chemical analysis of the mass spectrum, mimicking what instruments on the spacecraft will do. In particular, the results show that devices planned for future missions such as Surface dust analyzer (SUDA, Surface Dust Analyzer) on board the Europa Clipper can Recognize cell material into one of hundreds of thousands of ice grains.

Illustration of the Europa Clipper mission to Jupiter’s moon Europa. / NASA/JPL

They also used microorganisms. Although many studies use Escherichia coli In this case, another bacterium was chosen as a model, Sphingopyxis alaskensis, common in Alaskan waters. This single-celled organism is much smaller, lives in cold environments and can survive on few nutrients. All of these properties make it a better candidate for mimicking the potential life that could exist on the icy moons of Saturn or Jupiter.

“We use these bacteria because they are extremely small“Theoretically, they are able to fit into the ice grains that break off from oceanic worlds like Enceladus or Europa,” says Klenner, who, when asked whether completely different life forms could be detected, answers: “That would be very difficult, if.” You don’t know what to look for.

In any case, the results confirm that the instruments can detect Sphingopyxis alaskensisor parts of this microorganism, in a single grain of ice. The authors’ hypothesis is that if bacterial cells were wrapped in a lipid membrane like on Earth, they would also form a kind of “skin” on the surface of the subsurface ocean.

On Earth, sea foam is an important part of the marine aerosol that contributes to the smell of the ocean. On an icy moon where it is connected to the surface (e.g. above Cracks in the ice sheet), the vacuum of space would boil this ocean. Gas bubbles would rise and burst at the surface, where cellular material would become incorporated into ice grains within the outward-shooting cloud.

The left image shows the kilometer-thick ice crust thought to surround the moon Enceladus and one of its saltwater-filled cracks with a thin layer (in orange) on the surface. On the right you can see that as the gas bubbles rise and burst, they combine with organic material and are released into aerosols. / Postberg et al. (2018)/Nature

“Here we describe a plausible scenario of how bacterial cells can theoretically be incorporated into icy material that forms from liquid water on Enceladus or Europa and is then ejected into space,” says Klenner.

Which of the two moons would life be most likely on? “That’s a tough question, and both are incredibly tempting,” he replies. We know more about Enceladus because the Cassini mission has studied it in depth, and what we know about its potential as a habitat for life is remarkable. To date, there has been no Jupiter system mission dedicated to exploring Europa.”

SUDA instrument of the Europa Clipper mission

The Europa Clipper spacecraft will fill this gap thanks to the SUDA instrument, which will be able to detect this for the first time Ions with negative chargewhich makes them more suitable for detection Fatty acids and lipids. “For me, the search for lipids or fatty acids is more exciting than for DNA building blocks, since fatty acids appear to be more stable,” explains Klenner.

For his part, the lead author of the study, Frank Postbergprofessor of planetary science at the Free University of Berlin, adds: “With the right instrumentation, like the SUDA analyzer, finding life or traces of it on icy moons could be easier than we thought.” If, of course, life is present there and it wants to be trapped in ice grains from an environment such as an underground water reservoir.”

With the right instrumentation, like the SUDA analyzer on the Europa Clipper mission, it could be easier than we thought to find life or traces of it on icy moons, if it exists, of course.

Frank Postberg (Free University of Berlin)

Klenner summarizes: “That’s planned Europa Clipper is coming in 2030 to the Jupiter system, and I’m looking forward to your data on Earth. Until then, we will do everything we can to prepare for the success of this mission.”

Researchers from NASA’s Jet Propulsion Laboratory (JPL), the Open University of the United Kingdom, the University of Colorado at Boulder (USA) and the University of Leipzig (Germany) were also involved in this international study.

Luna Europa with its red stripes on the surface and target of the next Europa Clipper mission. / NASA/JPL/Galileo