Ice-encrusted moons of Saturn and Jupiter ‘could hold alien life’

By James Gamble via SWNS

The ice-encrusted moons orbiting Saturn and Jupiter are the most likely candidates for discovering alien life in our universe, scientists say.

Upcoming missions to Europa, an icy moon orbiting Jupiter, are believed to have what could be the greatest chance in history of identifying extraterrestrial life away from our planet for the first time.

Astronomers say ice grains ejected from the surface of the moons may contain enough material for the approaching missions to be able to detect signs of life.

American and German researchers add that newly available instruments and technology will make it easier to find lifeforms if they do exist.

The new study, published in the journal Science Advances and led by researchers at the University of Washington (UW) in Seattle and the Freie Universität Berlin, explores what this new generation of instruments may be likely to find.

NASA's Cassini mission, which ended in 2017, discovered parallel cracks near the south pole of Saturn’s icy moon Enceladus.

Plumes containing gas and ice grains were found to be emanating from these cracks.

NASA’s upcoming Europa Clipper mission, set to launch later this year in October, will carry more instruments to explore Jupiter's icy moon, Europa.

“For the first time we have shown that even a tiny fraction of cellular material could be identified by a mass spectrometer onboard a spacecraft,” said Dr Fabian Klenner, a UW postdoctoral researcher in Earth and space sciences and a lead author of the study.

“Our results give us more confidence that using upcoming instruments, we will be able to detect lifeforms similar to those on Earth, which we increasingly believe could be present on ocean-bearing moons.”

To prepare for the Europa mission, the study's researchers looked into what this new generation of instruments might be able to find.

As it's technically prohibitive to directly simulate grains of ice flying through space at four to six kilometers per second to hit an observational instrument, as the actual collision speed will be, the authors used an experimental setup that sends a thin beam of liquid water into a vacuum, where it disintegrates into droplets.

They then used a laser beam to excite the droplets and mass spectral analysis to mimic what instruments on the space probe would detect.

Results show that new instruments that will accompany future missions, such as the SUrface (corr) Dust Analyzer onboard the Europa Clipper, can detect cellular material in one out of hundreds of thousands of ice grains.

The study focused on Sphingopyxis alaskensis, a common bacterium in waters off Alaska.

Whilst many studies use the bacterium Escherichia coli as a model organism, this single-celled organism is much smaller, lives in cold environments and can survive with few nutrients.

These characteristics make it a better candidate for potential life on the icy moons of Saturn or Jupiter.

“They are extremely small," Dr Klenner explained, "So they are in theory capable of fitting into ice grains that are emitted from an ocean world like Enceladus or Europa."

Results showed that the instruments can detect this bacterium, or portions of it, in a single ice grain.

The new research shows that analyzing single ice grains, where biomaterial may be concentrated, is more successful than averaging across a larger sample containing billions of individual grains.

A recent study from the same researchers showed evidence of phosphate on Enceladus.

This planetary body now appears to contain energy, water, phosphate, other salts and carbon-based organic material - making it increasingly likely to support lifeforms similar to those found on Earth.

The authors theorize that if bacterial cells are encased in a lipid membrane like those on Earth, then they would also form a kind of skin on the ocean’s surface.

On Earth, ocean scum is a key part of sea spray that contributes to the smell of the ocean.

On an icy moon, where the ocean is connected to the surface through cracks in the ice shell, the vacuum of outer space would cause this subsurface ocean to boil.

Gas bubbles rise through the ocean and burst at the surface, where cellular material gets incorporated into ice grains within the plume.

“We here describe a plausible scenario for how bacterial cells can, in theory, be incorporated into icy material that is formed from liquid water on Enceladus or Europa and then gets emitted into space,” Dr Klenner said.

The SUrface Dust Analyzer onboard Europa Clipper will be higher-powered than instruments on previous missions and, along with future instruments, will for the first time be able to detect ions with negative charges - making them better suited to detecting 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," Dr Klenner said.

"The reason is because fatty acids appear to be more stable."

Senior author Frank Postberg, a professor of planetary sciences at the Freie Universität Berlin, added: "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.

"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.”