Unveiling Earth's hidden subterranean ecosystem

Presented at the 2018 American Geophysical Union's annual meeting, their groundbreaking research unveiled the staggering size of this hidden realm of life, surpassing all expectations.

According to their findings, around 70 percent of Earth's microbial population resides underground. This subterranean biosphere comprises 15 to 23 billion tons of carbon, dwarfing the carbon mass of all surface-dwelling humans by hundreds of times.

Despite our burgeoning knowledge, much about these microorganisms remains shrouded in mystery. Initial observations hint at genetic diversity comparable to, or even exceeding, that of surface life, earning the nickname "subterranean Galapagos" for this ecosystem.

Yet, don't anticipate encountering giant tortoises; bacteria and archaea reign supreme belowground, with the occasional presence of eukarya. In a South African gold mine, researchers even identified an unidentified nematode over 1.4 kilometers deep.

A decade ago, sampling efforts were limited to expected habitats, but advancements in ultra-deep sampling have unveiled life's ubiquity below the surface, albeit in a fraction of the deep biosphere. Sampling depths between 2.5 and 5 kilometers into the Earth's crust, researchers were astonished to find the subsurface biosphere nearly twice the volume of Earth's oceans.

Enduring extreme heat, crushing pressures, darkness, and scarce nutrients, the deep biosphere challenges conventional notions of habitability. Yet, it holds profound implications for understanding life's limits on Earth and beyond.

As microbial ecologist Rick Colwell of Oregon State University noted, the profound insights gleaned from deep biosphere studies underscore the boundless mysteries awaiting discovery. For now, scientists marvel at the resilience of life thriving under such inhospitable conditions.