A recent international study, led by Associate Professor Henrik Drake from Linnaeus University, has uncovered groundbreaking evidence that microorganisms lived deep beneath Greenland’s rocky surface 75 million years ago. This research offers new insights into the history of the “deep biosphere”, a hidden world of life existing far beneath the Earth’s surface.

The deep biosphere is a challenging environment for life. It exists hundreds or even thousands of meters underground, where sunlight is absent and dissolved oxygen is scarce or nonexistent. Microorganisms living in this environment have adapted to survive under these extreme conditions for millions of years.

Drake and his colleagues focused their research on the western part of Greenland, drilling deep into the bedrock to analyze fractures in the Earth’s crust. They discovered minerals lining these fractures, which serve as geochemical records of ancient life. Using a sophisticated dating method called calcium carbonate geochronology, the researchers analyzed how uranium within the carbonates decayed into lead over time. Their findings suggest that the microorganisms in these fractures existed between 64 and 75 million years ago.

Researchers extracted numerous cores drilling hundreds of meters deep in Greenland
Researchers extracted numerous cores drilling hundreds of meters deep in Greenland. Credit: Henrik Drake

These dates align with tectonic events that were precursors to the formation of the Atlantic Ocean and the Labrador Sea. It is believed that the tectonic shifts in Earth’s crust caused the deep fractures in western Greenland to open up, allowing water to flow through them. Along with the water came microorganisms, such as sulfate-reducing bacteria, which colonized these newly formed fractures. The study implies that the movement of continents has played a key role in the spread and colonization of microorganisms in the deep biosphere.

Henrik Drake describes the evidence found in the drill cores as “chemical fingerprints”, which indicate that life once thrived in this harsh environment. Moreover, the research team identified biological traces, such as bacterial fatty acids, preserved within the calcium carbonate crystals. These findings further support the idea that microorganisms inhabited these deep fractures millions of years ago.

To strengthen their conclusions, the researchers conducted thorough analyses of sulfur isotopes within minerals formed in the fractures. The results clearly show that these minerals were created through microbial sulfate reduction, a process in which bacteria reduce sulfate to obtain energy. This process is a well-known metabolic pathway for microorganisms living in oxygen-poor environments, further confirming the presence of ancient life deep within the Greenland bedrock.

This discovery not only expands our understanding of life in the deep biosphere but also raises new questions about how life has persisted in such extreme environments for so long. The deep biosphere, often compared to life on other planets, has been largely unexplored, with only small “pinpricks” of research conducted so far. This study adds an important piece to the puzzle, offering valuable insights into how tectonic movements and Earth’s shifting continents have influenced the spread of life deep within the planet.

SOURCES

Linnaeus University

Drake, H., Makahnouk, W. R. M., Roberts, N. M. W., Reinhardt, M., Henkemans, E., Frape, S. K., et al. (2024). Late Cretaceous and Early Paleogene fluid circulation and microbial activity in deep fracture networks of the Precambrian basement of Western Greenland. Geochemistry, Geophysics, Geosystems, 25, e2024GC011646. doi.org/10.1029/2024GC011646

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