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takyon writes:

Microbes Were Just Found in 'Dark Biosphere' Where They Shouldn't Exist

Thousands of feet below Earth's surface and far beyond the reach of sunlight, scientists recently discovered an unexpected form of life: microbes that typically produce their energy through photosynthesis.

Known as cyanobacteria, these hardy microorganisms have been around for billions of years, and though they're tiny, their photosynthesis prowess — in which they use the sun's energy to turn carbon dioxide into food for growth — played a big part in the planet's history. This activity helped shape a young Earth's oxygen-rich atmosphere, laying the groundwork for the emergence of all forms of life.

Today, cyanobacteria occupy a diverse range of environments, from baking deserts to oceans. But everywhere these organisms live, they typically get at least some exposure to sunlight. So, finding these creatures deep underground in total darkness was a big surprise, the researchers said.

In a prior expedition, the scientists had detected a rich subsurface ecosystem in the Iberian Pyrite Belt, an area along the Iberian Peninsula in southwestern Spain with enormous reservoirs of sulfide deposits. The researchers performed their second investigation deeper underground, in a previously untouched location at the same site. There, they targeted rocks that they anticipated would contain microbes closely resembling surface bacteria. They did not, however, expect to find cyanobacteria at a depth of 2,011 feet (613 meters). In fact, cyanobacteria were the most abundant organisms in the researchers' samples, the team reported in a new study.

Also at Space.com.

Viable cyanobacteria in the deep continental subsurface (open, DOI: 10.1073/pnas.1808176115) (DX)

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