Signs of Life Could Be Found Close to the Surface of Two Nearby Moons

Evidence continues to mount that life could theoretically survive in two moons currently orbiting planets in our solar system. Scientists have made a number of discoveries suggesting that Jupiter’s icy Europa moon and Saturn’s satellite Enceladus contain the conditions necessary for life. These include the production of ample amounts of oxygen on Europa and subsurface liquid oceans on both moons. Phosphorous, an element vital for life, has been found in plumes of ice and water ejected from Enceladus.

Now, a recent NASA experiment found that, if life does exist on these moons, signs of it, such as organic molecules like amino or nucleic acids, could be detected far closer to the surface than previously thought, despite incredibly battering radiation levels. That’s good news for any future missions that will search for signs of life sharing our Sun’s gravitational pull, as robotic landers would not have to drill deep to find it. 

“Based on our experiments, the ‘safe’ sampling depth for amino acids on Europa is almost 8 inches at high latitudes of the trailing hemisphere (hemisphere opposite to the direction of Europa’s motion around Jupiter) in the area where the surface hasn’t been disturbed much by meteorite impacts,” said Alexander Pavlov, a space scientist with NASA’s Goddard Space Flight Center in a press release. “Subsurface sampling is not required for the detection of amino acids on Enceladus – these molecules will survive radiolysis (breakdown by radiation) at any location on the Enceladus surface less than a tenth of an inch (under a few millimeters) from the surface.”

To figure this out, Pavlov and his colleagues took amino acids and mixed them with ultra-cold, -321 degree Fahrenheit ice. Other samples were combined not only with ice but silicate dust to simulate the potential presence of matter from meteorites or from deeper within the moons. Sealed in airless vials, the samples were hit with gamma rays, a form of hazardous radiation. Some other samples tested how the amino acids fared if they were implanted in dead bacteria, to simulate the possibility that there could be microscopic life on Enceladus and Europa. 

The results, published in the journal Astrobiology, showed the rate at which amino acids degraded in these conditions, and it turns out that they can survive long enough to be detected by a lander mission. No such mission is currently scheduled for either moon, however. 

“Slow rates of amino acid destruction in biological samples under Europa and Enceladus-like surface conditions bolster the case for future life-detection measurements by Europa and Enceladus lander missions,” said Pavlov. “Our results indicate that the rates of potential organic biomolecules’ degradation in silica-rich regions on both Europa and Enceladus are higher than in pure ice and, thus, possible future missions to Europa and Enceladus should be cautious in sampling silica-rich locations on both icy moons.”