Possible traces of life on Europa might be just a centimetre beyond our reach, suggests a paper published online this week in Nature Astronomy. Young regions at medium-to-high latitudes on the moon could be the best locations to look for such signatures, providing useful guidance for future Europa lander missions.

Jupiter’s moon Europa hosts a liquid ocean beneath its icy crust, making it a prime target in the hunt for extra-terrestrial life. Europa is immersed in a harsh radiation environment, however, which would quickly erase any trace of biological material on its surface. This has led to the suggestion that a lander sent from Earth would need to drill several metres into Europa’s hard crust to potentially obtain recognizable organic samples - an act presently beyond our capabilities.

Tom Nordheim and colleagues model the effect of energetic particles impacting Europa’s surface, and then compare these estimates with laboratory data on how quickly radiation destroys amino acids. The authors find that at mid-to-high latitudes amino acids could persist at detectable levels a mere 1-3 centimetres below Europa’s surface over a 10 million year time scale. At the more irradiated equatorial regions, however, this depth increases to several tens of centimetres.

The authors conclude that these results indicate that a future Europa lander might not need to dig too deeply to find potential signatures of life, provided that its landing region is well-chosen. Observations of Europa’s surface made with an orbiter or close-up flybys - like those of NASA’s planned Europa Clipper mission - will be key to identifying such regions.