Saturn’s icy moon Enceladus has long stood out as one of the most intriguing places in the solar system in the search for life beyond Earth. Beneath its frozen crust lies a global ocean of salty liquid water, and geyser-like plumes blast material from that hidden sea into space—offering scientists an unusually accessible glimpse of an extraterrestrial world. Now, new research adds another piece to the puzzle.
In laboratory experiments designed to mimic the harsh conditions thought to exist in Enceladus’ underground ocean, researchers have found that microbes from Earth can survive. The result does not mean that life has been found on Enceladus—but it strengthens the case that its subsurface ocean could, at least in principle, support life.
The findings are detailed in a new study published last week in Science Advances.
Icy world
At only about 310 miles (500 kilometers) across, Enceladus is about the size of Arizona and is believed to have a liquid water ocean beneath its frozen shell. While that alone doesn’t make it special, geyser-like jets erupting from its surface ice spray water from this ocean out into space, allowing spacecraft to sample its composition.
In 2015, NASA’s Cassini spacecraft flew through the water plumes shooting out of Enceladus’ shell at its south pole and found trace amounts of salt and organic compounds. Based on these samples, scientists determined that Saturn’s moon has most of the chemical ingredients needed for life.
To help find out if life could survive on Enceladus, the researchers behind the new study recreated the conditions of Enceladus’s ocean in a lab. They combined water with salts and carbonates and added powdered rock to reproduce the alkaline environment of the ocean, as well as the reactions that take place between the water and the rocky seafloor.
The researchers then threw in a microscopic species in the miniature alien ocean. Methanothermococcus okinawensis is a tiny living organism found near deep-sea hydrothermal vents in the Okinawa trough between Japan and Taiwan. It is also a methanogen, which is an organism that doesn’t need sunlight or oxygen to survive, but rather converts hydrogen and carbon dioxide into methane gas.
Surviving Enceladus
To their surprise, the researchers observed the organisms growing in the simulated Enceladus ocean by producing methane using hydrogen generated by water-rock reactions. The microorganism even adapted their metabolism to the low amounts of carbon dioxide in the alien environment.
“This was really a surprise to us,” Nozair Khawaja, a planetary scientist at Freie Universität Berlin who contributed to the study, said in a statement. “This was an experiment for which we did not expect such a successful outcome.”
In a second study published in the same journal, the researchers also suggest that it may be easier to find out what’s in the moon’s ocean than previously thought. Using Cassini data, the researchers found new evidence that suggest the plumes from Enceladus’ ocean freeze and fragments, separating the different compounds and minerals.
“Enceladus actually does a lot of the work for us in preparing samples for analysis that usually take a lot of effort in chemical labs on Earth,” Frank Postberg, planetary scientist at Freie Universität Berlin, who led the study, said. “The oceanic constituents are separated from each other and simultaneously concentrated into individual ice particles.”
According to Postberg, this is “great news in the search for life,” as future spacecraft exploring Enceladus could easily identify signs of life using current technology.
