The Role of Extremophiles in the Search for Extraterrestrial Life
We think life abounds beyond earth, a hypothesis that has been floating around for centuries. But locating such life is as challenging as finding a needle in a haystack, the haystack being the size of a planet or a star. How on earth are scientists preparing to overcome this formidable task?
The answer: by locating the driest, coldest, darkest, hottest, and saltiest environments on earth that mimic extraterrestrial environments, and getting to know their thriving inhabitants- the extermophiles- microbes that love environments deemed unlivable by most species.
Two such scientists are Biologist Jocelyne DiRuggiero at the Johns Hopkins University and astrobiologist Christopher McKay at the Space Science and Astrobiology Division at NASA Ames Research Center. On a Johns Hopkins University HUB webcast, the duo shed light on the various strategies employable for the discovery extraterrestrial life.
Jocelyne studies microbes living in the driest place on earth- the Atacama Desert of Chile, with areas that haven’t seen a drop of rain for as long as 400 years! Here, in an apparently parched, dead terrain, once described as the “most barren region imaginable, Jocelyne has found a diverse community of bacteria living inside rocks, many of them composed purely of salt.
Christopher, like Jocelyne, also studies extremophiles in- not the driest- but the coldest places on earth- the Antarctic dry valleys, where microbes can be found-again- living under rocks. “Living under rocks is a good strategy for microbes (in harsh environments),” describes Chris.
What can extremophils tell us about extraterrestrial life?
The idea is the many of these microbes have developed strategies to survive in extreme conditions, such as low moisture or low oxygen, some of which are comparable to the conditions on other planets such as Mars. Thus, these habitats can offer clues as to the kinds of places scientists should be exploring on foreign planets for signs of life, to essentially minimizing the size of the haystack.
Tools that are valuable in this quest are the same tools that scientists use to discover and identify new microbial species in extreme environments on earth- tools that can measure amino acids, lipids, and photosynthesis. Still, it is important to appreciate that extraterrestrial beings will likely not share the biochemical composition of Earthians, given the uniqueness of Earth’s atmospheric and elemental composition. Thus, new tools might need to be developed, catering to extraterrestrial environments, based on spectroscopy data on the atmosphere and gas composition of these foreign lands.
Regardless, the possibilities of the types of life on planets of our solar system as well as that on exoplanets are fascinating. Take Titan, for instance. This moon of Saturn has vast lakes and streams of liquid hydrocarbon, instead of water. Or Enceledus, another of Saturn’s moons, that likely has an underground ocean of liquid water. Perhaps life is cooking under these moist surfaces, bubbling away, the way it did a few billions years ago on Earth!