If life exists on the icy ocean moons of Enceladus and Europa, it could be that detectable trace molecules exist just beneath their frozen surfaces.
Scientists have long Enceladusone of Saturn’There are 146 known moons. Europeone of JupiterThe four big Galileo satellites the total The 95 moons could potentially host vast liquid oceans that could support life. amino acid and Nucleic AcidThis material, a building block of life as we know it, could act as a “biosignature” for life on the planet.
But the problem is that both Europa and Enceladus Sun This could destroy the complex organic molecules on the surface. But the new research suggests that traces of these organisms could survive if preserved in the moon’s icy shell. If this is true, these molecules would be so close to the surface that they could be detected in the future. Robot Lander In fact, on Enceladus, this drilling may not be necessary, since the biosignature molecules could survive in the ice, which is shallower than on Europa.
“According to our experiments, Europa Amino Acids “At high latitudes in the trailing hemisphere, the hemisphere opposite the direction Europa orbits Jupiter, in areas where the surface has not been disturbed much by meteorite impacts, it’s about 8 inches (20 centimeters),” said study leader Alexander Pavlov. National Aeronautics and Space Administration (NASA)Goddard Space Flight Center in Greenbelt, Maryland; It said in a statement“Detecting amino acids on Enceladus does not require subsurface sampling; these molecules survive radiolysis (breakdown by radiation) anywhere within less than a tenth of an inch (less than a few millimeters) of Enceladus’ surface.”
Related: If extraterrestrial life exists on Europa, it might be found in hydrothermal vents
Dramatic plumes of smoke erupt from Enceladus’ icy shell. Orbital Robot Mission It will be possible to collect these biosignature molecules from around Saturn’s moons without ever visiting the surface.
Life is deeply rooted on the icy moon
Europa and Enceladus are often cited as the planets other than Earth most likely to support life. Solar system, The likelihood of life existing on the surfaces of these moons is extremely low, not only because they are virtually atmosphereless and extremely cold, but also because they are covered in high-energy particles and radiation from the Sun. Cosmic rays From a powerful event Supernova Outside the solar system.
However, both Europa and Enceladus Liquid Water Ocean These moons have thick, icy surfaces that protect their oceans from such particles and keep them warm by geothermal heat generated by the gravity of their parent planets and their sibling moons.
This means that as long as these subsurface oceans have the right chemical reactions and energy sources, life could survive there.
To explore this, Pavlov and colleagues tested radioactive amino acids, which are produced by both biotic and abiotic processes, but what they found on Europa and Enceladus was Possible signs of life This is because amino acids are important building blocks of proteins for life on Earth, and it may be possible to extract amino acids from the deep oceans of these moons. Geyser Activityor by the churning motion of the ice shell itself.
The team took samples of the amino acids, sealed them in airless vials, and cooled them to about minus 321 degrees Fahrenheit (minus 196 degrees Celsius). The researchers then “detected” the amino acids.Gamma rays“We test the viability of the molecules” at different intensities.
The researchers also tested how well amino acids survived in dead bacteria trapped in the ice of Europa and Enceladus, to see what effect mixing them might have. Meteoritic material How does it affect their survival?
Taking into account the age of the ice on Europa and Enceladus, as well as the radiation environment surrounding both moons, the team was able to calculate how deep to drill and where 10% of the amino acids would survive radiolysis.
While these kinds of experiments have been done before, this particular test yielded two firsts.
This is the first time that researchers have examined the effects of exposing these molecules to low doses of radiation without completely breaking down the amino acids, leading the team to reason that even damaged or degraded molecules could serve as biomarkers. It is also the first time that such a test has examined amino acid viability along with amino acid survival. Meteorite dust.
The team found that amino acids decomposed more quickly when mixed with silica, similar to that found in meteorite dust, but the amino acids from the dead microbes decomposed at a slower-than-average pace, possibly because the bacterial cellular material protects the amino acids from reactive compounds produced by the microbes. Radiation attack If you don’t, it will deteriorate faster.
“The slow decomposition rates of amino acids in biological samples under surface conditions like those on Europa and Enceladus provide a basis for future life-detection measurements from Europa and Enceladus landing missions,” Pavlov said. “Our results indicate that the decomposition rates of potential organic biomolecules in the silica-rich regions of Europa and Enceladus are higher than in pure ice. Future missions to Europa and Enceladus should therefore be careful when sampling silica-rich sites on both icy moons.”
The team’s paper was published in the journal Neuroscience on Thursday (July 18). Astrobiology.
