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Piercing Europa’s surface : The use of a nuclear tunneler

Context : 

 

Europa, the fourth biggest moon of Jupiter, has a gigantic ocean under its surface, containing salty water, more than all our oceans combined. Therefore, we planned to search for life inside.



Image of Europa, taken by NASA’s Juno spacecraft, 2022. Credit: NASA 
Image of Europa, taken by NASA’s Juno spacecraft, 2022. Credit: NASA 

Why is it more promising to search for life on Europa than on Mars ? 

 

The research done aims to prove the previous existence of life on Mars and ideally find some of it fossilized somewhere on its desertic surface. However, the chances of finding something are very low, or close to non-existent, while Europa provides the required conditions to sustain present life. It has a thick icy surface of two to thirty kilometers which protects from radiation, high energy electrons and heat sources produced by the strong tidal forces induced by Jupiter’s huge mass. This heat can be, alongside chemical nutrients, a source for some life forms just like around hydrothermal vents on Earth. 


 The ways to find life, and the obstacles :


 Ways to go through the surface 

 

Artist's view of a probe to find life on Europe. Credit : Alexander Pawlusik, LERCIP Internship Program NASA Glenn Research Center
Artist's view of a probe to find life on Europe. Credit : Alexander Pawlusik, LERCIP Internship Program NASA Glenn Research Center

Europa presents conditions for life, but only under it’s surface. We could try to only search life in the geyser's water, although water could take several centuries, or even millions of years to come to the surface. Because of this, we would probably only have fossils or traces of life from far in the past, without indications of present life. So, we need to reach the ocean underneath, and pierce through kilometers of ice, if we don’t find underground lakes while going down. Once the probe reaches the liquid water, it would take samples in order to allow us to study it. Although there are some problems to it: being deep into the surface would make us unable to communicate with it, and melting the ice drains a tremendous amount of energy. 

 

Andrew Dombard and his collegues, from the NASA Glenn Research Center, came up with two solutions. The first consist in a radioactive battery, powered with a plutonium-238 dioxide solution used by the probes Galileo and Cassini, or directly melt ice with self-heating radioactive bricks. The second solution consist in an « upgraded nuclear reactor », which would involve a thick shielding to prevent the radiations from altering results, destroying the samples or even damaging the probe itself.



Both of these solutions still have to be paired with a « hanging » system to prevent the probe to fall into the pit upon reaching it’s goal, being held by a module securely anchored to the surface. This module would serve as a relay between the earth and the probe, connected to it with reinforced optical fiber cable to survive ice shifts, and radio repeaters each 5 km as a failsafe.


Concept of a swarm of tiny bots. Credit : NASA/JPL-Caltech
Concept of a swarm of tiny bots. Credit : NASA/JPL-Caltech

The solutions described above help to reach the water to take samples, but the heat produced by the probe may affect the results, preventing any viable research. Ethan Schaler, a robotic mechanical engineer at NASA’s Jet Propulsion Laboratory, proposed the idea of miniaturized robots to gather more samples, far from the mother probe. Those robots would only take about 15% of the science payload volume. This solution also allows to measure gradients, which are the most common ways for primitive life forms to obtain the necessary energy. To achieve this, they can be coordinated to simultaneously take data from different locations.






Requirements for the mission 

 

In order to find a proper landing site on Europa’s surface, with a thin enought surface, it is necessary to gather more data, as Europa’s surface is not well-mapped. We have the mission Europa Clipper for future better mapping. Although, after this mission, it is still needed to think of a way to send the probe that would pierce through the surface. 

 

Alternative solutions 

 

As we can’t send a probe of this weight for now, it is also important to consider another solution, imagined by the physician Freeman Dyson. His idea comes from the fact that Europe’s convections currents continuously regenerates the surface’s ice, especially at the equatorial area where the ice is thin. It also explains the absence of visible asteroid impacts on it’s surface, but would also mean that those impacts could send some ice containing life forms into space. We could then study those ice blocs instead, as we studied moon’s samples from meteorites found on earth. 



Artist's view of Europa's surface, with ice diapirs going up under a chaotic terrain. © Nasa, JPL-Caltech
Artist's view of Europa's surface, with ice diapirs going up under a chaotic terrain. © Nasa, JPL-Caltech

Conclusion : 

 

All the ideas that we have described are hopes to find something under the surface of this giant frozen moon, but in order to even consider such solutions. We might have to develop more advanced technology and knowledge, let’s hope that it will come soon. 


Sources : 

 

 

Cover picture of the article from Getty/NASA 


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