The dark, high-pressure depths of Earth’s interior is an unexpected place to find life. Now, an international group of scientists report there’s 16.5 to 25 billion tons of micro-organisms beneath the planet’s surface. The team’s work is redefining what a habitable environment is.

The discoveries “force us to reimagine what the boundaries are that life can exist in,” said Karen Lloyd, a microbiologist at the University of Tennessee in Knoxville.

Deep Discovery
Lloyd is a member of the