BOSTON – It sounds like a sci-fi tale: Scientists manage to revive strains of microbes that have been trapped inside giant cave crystals for tens of thousands of years, and find out that they seem positively alien.
But this tale is totally real. And although these organisms are so unlike anything else on Earth that they haven’t yet been given a genus or species name, they’re totally terrestrial.
“They’re really showing us what our kind of life can do,” said Penny Boston, director of the NASA Astrobiology Institute.
Boston told the tale of the creatures found in Mexico’s Naica cave complex today in Boston at the annual meeting of the American Association for the Advancement of Science. She and her colleagues haven’t yet published their findings, but they’re closing in on the final analysis.
“We are hysterically persnickety and conservative,” she told reporters. “We never rush to press.”
Boston and her colleagues have been working on the project since 2008, when they made their way into the depths of Naica’s crystal caves to look for “extremophiles” – that is, organisms that can thrive in extreme environments. Learning how extremophiles survive could someday help scientists search for life on Mars or within the seas of Europa, an ice-covered moon of Jupiter.
The conditions inside the caves in Mexico’s Chihuahua state are definitely extreme: For millennia, the chambers were filled with mineral-rich, geothermally heated water. That fostered the formation of gypsum crystals measuring up to almost 40 feet in length.
As the crystals formed, tiny pockets of water became trapped within the mineral layers. Less than two decades ago, the water was pumped out of the caverns to clear the way for silver, zinc and silver mining, leaving the crystals behind.
For decades, Boston has studied extremophiles found in caves, so Naica was a natural for her. “It’s one of my specialties – growing weird bugs on weird stuff,” she said.
Exploring the caves was “a transformative experience, in a really horrible sense,” Boston said. The researchers had to wear bulky ice-cooled suits to work amid temperatures that ranged as high as 140 degrees Fahrenheit. The deepest chamber, lying a half-mile below the surface, was nicknamed “Hell.”
Boston’s team braved the heat, drilled into the crystals and extracted samples from the trapped pockets of water, taking care to avoid contamination. An analysis of the deposition rates for the crystal layers led researchers to conclude that the water had been trapped for anywhere between 10,000 and 50,000 years.
The researchers were amazed to find dormant microbes in the water samples. In the lab, Boston was able to get several strains to grow by feeding them a mix of minerals.
“Primarily, they’re bacteria,” she said. “Some of them are sulfide users. Some of them are sulfate reducers. Some of them are good old heterotrophs. Some of them are iron oxidizers. … Some of those are getting at least part of their energy from the oxidation of manganese.”
Still more amazement ensued when the microbes’ DNA was analyzed. The genetic sequences weren’t a close match for any previously known organism. Even the closest match was still 10 percent different in its detailed DNA coding.
“Their closest relatives are weird things like organisms in other caves halfway around the world, or volcanic soils in Kamchatka,” she said.
Boston is still studying exactly how the microbes function. She noted that other types of extremophiles have been harnessed to produce new antibacterial drugs or cancer-fighting chemicals, but it’s not known whether that could be the case for the Naica microbes.
“If somebody wants to tap into it, good,” Boston said. “Whether or not that would ever lead to actual drug discovery or anything like that, we have no idea. That’s not our bag.”
Her bag has more to do with how life gets by on Earth, and perhaps on other worlds as well. Maybe one of the secrets to life’s success is simply its ability to “hang out” and wait for a more hospitable environment when the going gets tough, she said.
“If you imagine organisms being geologically stored for random amounts of time, and then reintroduced … essentially, you have forward time machines,” Boston said.
John Rummel, a biologist at the SETI Institute who has also served as NASA’s planetary protection officer, agreed that the results suggest life can be weirder than we know it. And there may be more surprises to come.
“Only complete hubris would drive you to say, ‘Yeah, we found that one, but now we know everything,'” he said.