New types of bacteria have been found in one of the most alien environments on Earth: a subglacial lake buried beneath almost a thousand feet of ice. This far removed from sunlight and air, conditions could be strikingly similar to the subterranean oceans of Europa or Enceladus, so studying the microorganisms that call this inhospitable place home could aid the search for extraterrestrial life.
They might not seem particularly inviting for human settlers, but the oceans beneath the surfaces of Jupiter's and Saturn's moons are among the most promising places to look for life beyond Earth. Both Europa and Enceladus are spraying huge plumes of ice and water into space, and analyses of the Enceladus jets have found that the basic necessities for life are present and accounted for.
"By flying through the water-rich jets, the Cassini spacecraft has detected complex organic molecules as well as hydrogen, making Enceladus one of the most potentially habitable environments in this solar system," says Dr Gabriel Tobie, a planetary scientist from the University of Nantes in France.
The team has previously used mathematical modeling to map the thickness of Enceladus' icy crust, and found that it could be as thin as 5 km (3.1 mi) at the poles. Not only would that make it more viable for potential landing missions to dig down to the waters, but it provides further evidence of life-favoring conditions down there.
"This thinner crust implies that there is a huge heat source at this moon's interior which may power hydrothermal vents on the floor of this underground ocean," says Tobie.
The findings are encouraging enough that NASA is planning missions to probe the icy waters inside both moons, with the primary mission of seeking out direct signs of life. But before then, it would help to have a solid idea of what to look for.
Enter AstroLakes. Funded by the European Union, this research project is studying life in Skaftárkatlar, a subglacial lake in Iceland, as a possible analog for exoplanet oceans. Sitting under 300 m (984 ft) of ice, it's likely the waters there have never seen sunlight or been exposed to the atmosphere, which makes them great candidates for studying distant alien oceans.
The team took 10 samples of this subglacial water in 2007, 2014 and 2015 by pumping hot water down to melt a narrow column of the ice, then collecting the water that gathers at the bottom. So far, the team has found evidence of previously-unknown bacteria, and studying how they might have evolved under these conditions could help scientists spot similar lifeforms on Europa or Enceladus.
"Our preliminary results reveal new branches of life here," says Gregory Farrant, lead investigator on the AstroLakes project. "It's tricky to analyse DNA of microbes that are totally new to science because there's no prior knowledge about them. We're dealing with a lot of unknowns."
The project is expected to continue until May 2018, and will involve sequencing Skaftárkatlar's metagenome, the broad pool of genetic material from a range of organisms that live in the glacial lake.