Miles below the icy surface of Jupiter’s moon Europa, there is an ocean that likely contains more water than all the seas on Earth. This intriguing marine environment has distinguished Europa as one of the most promising candidates to host alien life in the solar system.
But there’s a catch: The moon is blasted by Jupiter’s intense radiation, so any biological material exposed on its surface would be damaged, perhaps beyond recognition. That presents an obvious challenge for future lander missions seeking signs of life in Europa’s outer crust.
Fortunately, research published Monday in Nature Astronomy finds that radiation exposure varies widely on Europa, which will help scout out the best sites for potential life. Led by Tom Nordheim, a research scientist at NASA’s Jet Propulsion Laboratory, the study found that the moon’s mid-to-high latitudes are exposed to lower radiation doses than the equatorial regions, which get pummeled by energetic electrons in patterns called “radiation lenses.”
Landing sites at these higher latitudes could support traces of life—or “biosignatures”—within one to three centimeters of the surface.
The team also calculated that biosignatures could survive at accessible depths practically anywhere on Europa. “Even at the worst possible places, you only have to dig about 10 to 20 centimeters,” Nordheim told me in a phone call. “You only have to scratch the surface.”
These speculative biosignatures would probably not be living organisms, but biological fragments—organic compounds, amino acids, or perhaps cellular material—that originated in the subsurface ocean.
According to Cynthia Phillips, deputy project scientist for NASA’s Europa Lander mission concept, it will take “multiple complementary lines of evidence” to distinguish whether these samples are truly remnants of aliens from the Europan deep.
“It would be really nice if we had a _Star Trek_-style tricorder that you could just point at something and it would say: ‘it’s life,’” she told me in a phone call. “Unfortunately, we haven’t invented one of those yet.”
Instead, the Europa Lander team envisions a scientific payload with cameras and seismometers for situational awareness on the surface, coupled with spectrometers and microscopes that could mine chemical and structural information from samples. The mission concept also included a drill that could extract samples to depths of about 10 centimeters.
“You would be able to look at not just the composition but also the microscale structures [...] that might be indicative of life,” Phillips said.
This sophisticated, multipronged approach to biological detection, combined with the discovery that traces of life could be accessible to proposed spacecraft like Europa Lander, makes this fascinating ice moon an even more tantalizing target in the search for extraterrestrial life.
“When you see those images of Europa,” Nordheim said, “with all those cracks and brownish-red material, the idea that we could actually go there and sample that and look for biosignatures and the composition of the ocean—that’s very appealing.”
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