Experimental setup reveals signs of life in single ice grain from extraterrestrial moons

March 22, 2024

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According to a laboratory study led by the University of Washington, Seattle, and Freie Universität Berlin, the icy oceans on several moons around Jupiter and Saturn are prime targets in the search for life beyond Earth. The study reveals that individual ice grains released from these celestial bodies could contain enough material for the instruments heading there this fall to detect potential life.

Fabian Klenner, a University of Washington postdoctoral researcher in Earth and Space Sciences and the leading author, stated: 'We demonstrated for the first time that even a tiny fraction of cellular material could be identified by a mass spectrometer onboard a spacecraft.' He emphasized their growing belief in the presence of lifeforms similar to those on Earth, on these ocean-bearing moons.

Science Advances published the open-access study. Other contributing international team authors include academics from The Open University (UK), NASA's Jet Propulsion Laboratory, the University of Colorado, Boulder, and the University of Leipzig.

The Cassini mission that concluded in 2017 discovered cracks near Saturn's moon, Enceladus's south pole. These cracks are releasing gas and ice grains. The Europa Clipper mission by NASA, set to launch in October, will be equipped to explore further Jupiter's icy moon, Europa.

Researchers are preparing for this mission by studying what these next-generation instruments might discover. The experiment involved an innovative setup including a thin beam of liquid water being sent into a vacuum, where it breaks down into droplets, excited by a laser beam. Mass spectral analysis was then used to simulate what future space probes will detect.

The study findings show that forthcoming mission instruments, like the SUrface Dust Analyzer on the Europa Clipper, can detect cellular material in one out of hundreds of thousands of ice grains.

Sphingopyxis alaskensis, a typical bacterium found in Alaskan waters, was used in this study. Researchers prefer this over the oft-used bacterium Escherichia coli, as it thrives in cold environments, needs few nutrients, and is significantly smaller, making it an ideal potential life candidate on Saturn's or Jupiter's icy moons.

Klenner stated: 'These bacteria are extremely small, fitting into ice grains released from ocean worlds like Enceladus or Europa.'

The study found that it is more effective to analyze individual ice grains, where biological material might be concentrated, than averaging across a large sample containing billions of individual grains. Their instruments can detect this bacterium or parts of it in a single ice grain, with different molecules ending up in different ice grains.

An earlier study led by the same researchers discovered evidence of phosphate on Enceladus. This celestial body now appears to support lifeforms similar to those on Earth, as it potentially possesses energy, water, phosphate, other salts, and carbon-based organic material.

Bacterial cells might form an outer skin on the ocean's surface if encased within a lipid membrane, similar to those on Earth. This skin on Earth contributes to sea spray and the smell of the ocean (ocean scum). On an icy moon where the ocean is linked to the surface (like through ice shell cracks), a vacuum in outer space would cause this subsurface ocean to boil. This would result in gas bubbles traveling through the ocean and bursting on its surface, leading to cellular material inclusion within the ice grains of the plume.

'We propose a feasible scenario for how bacterial cells might be incorporated into icy material that forms from Enceladus or Europa's liquid water and then gets released into space,' Klenner said.

The SUrface Dust Analyzer on Europa Clipper and future instruments will have higher power than devices on previous missions. They will also detect negative ions for the first time, improving their ability to identify fatty acids and lipids.

'For me, it is even more exciting to look for lipids, or for fatty acids, than to look for building blocks of DNA, and the reason is because fatty acids appear to be more stable,' Klenner said.

'With suitable instrumentation, such as the SUrface Dust Analyzer on NASA's Europa Clipper space probe, it might be easier than we thought to find life, or traces of it, on icy moons,' said senior author Frank Postberg, a professor of planetary sciences at the Freie Universität Berlin.

'If life is present there, of course, and cares to be enclosed in ice grains originating from an environment such as a subsurface water reservoir.'

Journal information: Science Advances , Nature

Provided by University of Washington