NASA researchers made a rather bombshell discovery when they learned that just beneath the icy skin of Jupiter’s moon Europa and Saturn’s moon Enceladus could be located amino acids, possible indicators of life. Such findings could very significantly alter how future missions to detect extraterrestrial life are carried out, possibly in such a way as to not require robotic landers to drill quite so deep to find these organic molecules.
The Allure of Icy Moons
Interest in Europa and Enceladus has never been low among researchers, given the thick polar ice crusts concealing liquid water oceans beneath. It would not seem fantastic to imagine life thriving in these water bodies, heated by tidal forces from their host planets and neighboring spheroids, providing they have the essential elements and compounds to support it. Newly published experiments by NASA show that even if life does exist in these dark oceans, signs of it, such as amino acids, could persist right next to the surface ice despite the strongly irradiating environment.
According to Alexander Pavlov of NASA’s Goddard Space Flight Center, lead author on the study published in the journal Astrobiology, this “safe” depth for sampling Europa for amino acids is almost 8 inches (about 20 centimeters) at high latitudes of the trailing hemisphere, where meteorite impacts don’t significantly perturb the surface. He further stated that in the case of Enceladus, subsurface sampling wouldn’t be necessary to identify amino acids because these molecules could survive radiolysis anywhere on the surface of Enceladus down to a depth of less than one-tenth of an inch.
Experimental Results
The researchers completed some experiments regarding the radiolysis of amino acids representing biomolecules. For terrestrial organisms, amino acids produced both biologically and non-biologically link to form proteins, which according to experts, are basic elements of life. The team combined samples of amino acids with ice chilled to nearly minus 321 degrees Fahrenheit (-196 degrees Celsius) inside sealed, airless vials and zapped them with gamma rays to see if they could survive on such moons. They also explored the survival of amino acids in devitalized bacteria in pure ice and ice doped with silicate dust, to simulate mixing of meteoritic or lunar interior material with surface ice.
These experiments provided the basic data from the radiolysis constants, which set the rate of decomposition of amino acids. Then using these rates the authors modeled the drilling depths and sites of 10% of the amino acids that would still be preserved from radiolytic degradation. Pavlov stated the implications of the results: Such slow destruction rates of amino acids in biological samples in conditions that are similar to the surfaces of Europa and Enceladus make an even stronger case for future in situ life-detection measurements of the Europa and Enceladus landers.
Implications for Future Missions
The results suggest that future missions to Europa and Enceladus could detect amino acids, simply, without deep drilling, the searches for life become much simpler. According to Pavlov, indicated rates of possible organic biomolecule degradation in the silica-rich region in both Europa and Enceladus are higher than they are in pure ice, a suggestion for future missions to be quite wary of silica-rich locations on the sampling of these icy moons.
This affords a basis for the proper planning of any future missions related to the radiation environment and the composition of the surface ice. In general, this work points out some potential major life-detection discoveries with missions only requiring sampling at relatively shallow depths of the subsurface.
They also revealed that when mixed with dust, amino acids broke down while being derived from microorganisms. This may point out the fact that bacterial cellular material protects the amino acids against reactive compounds produced by radiation. Pavlov pointed out that bacterial cellular material protects amino acids from the reactive compounds that the radiation produces.
Such protective mechanisms may be crucial to the preservation of biomarkers in the harsh environments of Europa and Enceladus so that if there are signs of life, the chances of successfully detecting them are high.
Therefore, the results set a very firm platform for further research and mission planning in the search for life on icy moons. Knowing more precisely how amino acids and other organic molecules can survive under these conditions can help researchers design better instruments and sampling strategies for future missions. Further exploration of Europa and Enceladus will continue to probe a wealth of secrets from these captivating worlds, pushing the search for life far beyond Earth.