Evrim Yazgin
Cosmos science journalist
A new lab-based study shows that a single grain of ice – blown into space by subsurface boiling – could contain enough material to detect signs of life on one of the moons in our solar system.
An instrument that has this capability is going to be launched in the direction of some key candidates later this year.
Ice-encrusted oceans of some of moons in our solar system are the leading candidates in the search for extraterrestrial life.
Jupiter and Saturn are known for their moons – constantly stripping each other of the title of most moons in the solar system. But it’s more than just a numbers game when it comes to the satellites orbiting these gas giants.
Before ending in 2017, NASA’s Cassini mission discovered cracks near the south pole of Saturn’s moon Enceladus from which plumes of gas and ice were being ejected.
A new NASA mission, named Europa Clipper, is set to launch in October. It will carry more instruments, such as the SUrface Dust Analyzer (SUDA), to explore in even more detail the icy Jovian moon Europa.
Researchers studying the instruments have published their findings in the journal Science Advances.
Rather than recreating the SUDA passing through plumes of ice traveling 4–6 km/s, the scientists simulated what the instrument would see by firing a laser beam at droplets to mimic what the instrument would see.
They focused on Sphingopyxis alaskensis, which is a bacterium commonly found in waters off Alaska.
Normally, studies use Escherichia coli as a model organism. S. alaskensis lives in cold environments and can survive with few nutrients, making it more suited to simulating potential life on icy moons.
“They are extremely small, so they are in theory capable of fitting into ice grains that are emitted from an ocean world like Enceladus or Europa,” says lead author Fabian Klenner from the University of Washington.
“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,” Klenner says. “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.”
The same researchers published another study last year on their discovery of phosphate on Enceladus. The fact that the icy moon appears to have energy, water, phosphate, other salts and carbon-based organic material suggests it could harbour life similar to that on Earth.
They believe bacteria on other worlds could be encased, like single-celled organisms on Earth, in a lipid membrane. Remnants of these membranes could form a film on the surface of the ocean which could be emitted into space when the vacuum of outer space causes the subsurface ocean to boil and eject in great plumes.
“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 says.
“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,” Klenner adds.
