Extremophiles hint at possible resilience of life beyond Earth
BOSTON — Microbes found stowed inside giant crystals in caves in Chihuahua, Mexico, may have survived there for tens of thousands of years. The microorganisms, which appear to be vastly different from nearly all life-forms found on Earth, offer a good indication of how resilient life can be in extremely harsh environments, including those found on other planets.
“These organisms are so extraordinary,” astrobiologist Penelope Boston said February 17 during a news conference at the annual meeting of the American Association for the Advancement of Science. They are not close to any known genus scientists have been able to identify, said Boston, director of the NASA Astrobiology Institute in Moffett Field, Calif. Their closest relatives live in caves halfway around the world or in volcanic soils or thrive on compounds such as toluene.
For eight years, Boston and her colleagues have been studying microbes deep inside the Naica lead, silver and zinc mine. Some microorganisms were discovered trapped in fluid pockets inside massive crystals of calcium sulfate. Analysis suggests that the microbes may have been tucked away in these tiny time capsules for 10,000 to 50,000 years and may have been dormant for some or all of that time. But they “remained viable in some fashion and were able to be regrown,” she said. Her team reawakened the microbes in the lab and studied their genetic material, along with genetic material from other organisms found in the walls of the cave and other areas near the crystals.
The microbes found inside the crystals appear to be similar but not identical to those living outside, on the cave walls and other nearby areas, Boston said. That leaves Boston and her team fairly confident that the samples were not contaminated with other microbes and that their age estimates for the crystal-trapped microbes is solid. The team has not yet published the result. If confirmed, the microbes would represent some of the toughest extremophiles on the planet — dwelling at depths 100 to 400 meters below Earth’s surface and enduring temperatures of 45° to 65° Celsius.
“Any extremophile system that we’re studying actually allows us to push the envelope of life further,” Boston said. “We add it to this atlas of possibilities that we can apply to different planetary settings.”
Studies like these show that some microbes are hardy creatures, willing to turn just about any habitat into a home. That’s promising for the hunt for life beyond Earth. It’s problematic, however, as researchers start to think about sending probes to potentially habitable worlds, such as Jupiter’s moon Europa and Saturn’s moon Enceladus. Boston’s discovery is a reminder of how little scientists know about the microbes on Earth. And that means there are unknowns about what life-forms could stow away on spacecraft sent to other worlds, says Cassie Conley, NASA’s planetary protection officer.
“If you took some of these organisms from Earth and put them elsewhere, they may do just fine,” she says. That’s not so great for studying any native life that might be there. The Earth-based life could take over and contaminate those worlds.
P. Boston. The astrobiological exploration of Earth and Mars. American Association for the Advancement of Science annual meeting, Boston, February 17, 2017.
R. Ehrenberg. Life under ice. Science News. Vol. 184, September 7, 2013, p. 26.