Jordana Cepelewicz writes:

Microbial life, almost unbelievably resilient, abides in boiling hot springs and bone-dry deserts, in pools of acid and polar ice, kilometers up into the sky and kilometers below the ocean floor. And while scientists are eager to uncover microbes in even less familiar territories beyond our solar system, it’s the last Earth-bound frontier on that list — the deep subsurface — where they’re now making exciting progress in their efforts to probe life’s extreme adaptability.

Lightless, barren of essential nutrients and crushed under inconceivable pressures, the deep subsurface seems unrelentingly inhospitable, yet it is shaping up to be one of Earth’s biggest habitats. Moreover, its strangeness is forcing scientists to reckon with biological systems that operate on completely different energy sources and time scales from those that we surface dwellers are accustomed to.

Scientists have spent decades studying how and where microbes persist and even thrive beneath the oceans, far removed from the sun. Most of that work has focused on marine sediments, the tightly packed mud and detritus that in places extends for kilometers beneath the water. But there’s also the volcanic rock below that, the crust itself. The life in those rocks is much more difficult to access and analyze, and samples are scarce.

“We do not have a map of the deep subsurface microbial landscape right now,” said Karen Lloyd, a microbiologist at the University of Tennessee, Knoxville. As a result, she noted, researchers studying its diverse range of environments can’t even make simple generalizations equivalent to “forests have trees and fish swim in the oceans.”

But a handful of new discoveries has finally opened a window onto that landscape and the microbes that inhabit it. It has also offered a glimpse into the very origin and evolution of life, both on this planet and possibly elsewhere in the universe. [Continue reading…]