A hidden ecosystem teeming with microbial life deep inside the Earth could be far more vast than suspected, operating entirely without input from the sun, according to new research.
Scientists have found the organic signatures of this strange microbial world in the warm fluid that slowly circulates through basalt, porous rock buried deep under the ocean floor.
"These microbes live without sunlight or photosynthesis — they get their energy from the rocks, and they get their carbon from the fluid around them," said Matthew McCarthy, associate professor of ocean sciences at the University of California, Santa Cruz.
Instead of looking for the microbes themselves, McCarthy said, he and his team retrieved and studied molecules dissolved in the warm stew of liquid percolating through the basalt, because that hydrothermal fluid and the molecules it contains are chock full of clues about a larger microbe civilization.
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"When you look at the microbes, they tend to tell you about what's going on right at the spot where you're sampling," McCarthy told OurAmazingPlanet. "The dissolved molecules tend to be the leftovers of entire ecosystems. What's in there is basically a fingerprint for these huge systems under the crust."
And it is precisely the possible scale of these microbial ecosystems that's the real surprise, McCarthy said.
It's well established that life can go on independent of help from the surface world.
However, those vents are few and far between. Basalt, on the other hand, is abundant beneath the Earth's surface.
"Our work doesn't say for sure that this is worldwide, but it's the strongest piece of evidence yet to suggest that, yes, there is a huge biosphere down there," McCarthy said.
Not only does this hidden ecosystem appear to operate entirely on its own, it appears to be sending organic molecules up into the ocean.
This could have large implications, if the deep microbial biosphere is as vast as this research suggests. It could change oceanographers' entire understanding of ocean biochemistry and the mechanisms that govern the processing of the planet's carbon.
"Our understanding of the ocean carbon cycle is predicated on the idea that everything we measure came from stuff on the surface and photosynthesis," McCarthy said, "and if that's not true, that changes a lot. This work doesn't show that's true, but it changes it a lot."
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