Could Saturn's Moon Enceladus Host Alien Life? Earth Microbes Can Live in Its Simulated Environment, Boosting Its Potential Habitability

Saturn’s moon Enceladus is one of astrobiologists’ favorite places in the solar system. Geysers spray salty ice from its south pole, hinting that the world harbors an underground ocean—and it might have the ingredients to spawn life. Now, two studies published September 25 in the journal Science Advances may have boosted our understanding of Enceladus’ potential habitability and our ability to assess it.

One revealed that an Earthly microbe can survive in conditions simulating the distant moon’s ocean. The other found that if life exists on the watery world, it might be easier to detect in samples than previously thought. Future spacecraft that go there and collect plume particles could identify signs of life “relatively easy with already available technology.” In the Earthly microbe study, Postberg and colleagues investigated Methanothermococcus okinawensis, a methane-producing, heat-loving archaeon found in deep-sea hydrothermal vents.

They stuck it in a lab-made solution of water, salts, carbonates and powdered rock to mimic the environment of Enceladus’ seafloor, specifically vents there. The concoction had little oxygen and was a pH of 11, meaning it was highly alkaline, a condition that most known organisms can’t endure. Nevertheless, M. okinawensis persisted.

The microbes grew in the Enceladus-like slurry, adapting to the solution’s low level of carbon dioxide and using hydrogen produced by the water-rock reactions to fuel themselves. That involves a biological process called methanogenesis, which makes methane as a byproduct. Another heat-loving microbe A recently discovered organism called the “fire amoeba” also survives at sweltering temperatures.

Unlike archaea, the amoeba belongs to the more complex group of life called eukaryotes, which have membrane-bound organelles, such as nuclei and mitochondria, in their cells. The fire amoeba can swim around at a sweltering 147 degrees, setting a new heat record for complex life. The other study, meanwhile, investigated how challenging it would be to detect microbial life in material spewed from the distant moon’s subterranean ocean.

Previous research suggests that after gas bubbles rise to the top of the ocean and pop, water vapor transports liquid droplets through cracks in the outer icy shell and into space, creating the famous plumes. Using lab experiments and thermodynamic calculations, the researchers found that, contrary to previous ideas, these droplets freeze slowly, causing most of their dissolved ingredients to separate from one another. That means components like salts and organic materials within each frozen droplet would be organized in distinct locations, rather than being enmeshed.