What's New
Scientists have discovered astonishing microbial diversity deep beneath Earth's surface, which could have implications in the hunt for life on Mars.
The study, published in Science Advances, examined microbes from up to 3 miles underground and 1,600 feet beneath the seafloor.
These organisms thrive in extreme, low-energy environments—conditions that could mirror those on Mars or other planets with subsurface ecosystems.
Led by Emil Ruff, the research is the first large-scale comparison of marine and terrestrial subsurface microbiomes, offering a glimpse into the possible adaptations of alien life.
Why It Matters
The findings have important implications for the search for extraterrestrial life.
If Mars or other rocky planets ever had liquid water beneath their surfaces, the ecosystems there might resemble Earth's deep biosphere.
The study also highlights how life can persist with minimal energy, with microbial cells diving far slower than they do at the surface.
Understanding these adaptations could refine future astrobiology missions in the quest to find signs of life.
"It's fascinating that, in these low-energy environments, life seems to be slowed down to an absolute minimum," Ruff said in a statement. "Some subsurface cells divide only once every 1,000 years. So, these microbes have completely different timescales of life."
What to Know
Microbes in Earth's subsurface have evolved to survive with almost no energy. Their metabolism is fine-tuned to be incredibly efficient.
The research revealed that microbial diversity underground can rival or even exceed that of surface ecosystems, such as coral reefs.
Scientists estimate between 50 and 80 percent of Earth's microbial cells may live in these subterranean ecosystems.
"We can now also appreciate that perhaps half the microbial diversity on Earth is in the subsurface," Ruff said.
These environments are inhospitable places to live, with little energy or warmth to keep biological processes going.
"It makes sense to be evolutionarily adapted to absolutely minimize your power and energy requirements and optimize every single part of your metabolism to be as energy efficient as possible," Ruff said.
"And we can also learn from that: How to be extremely efficient when you are working with next to nothing."
Mars itself was once covered in water, and the rocky ecosystems evaluated in this study likely mirror those miles beneath the surface of the red planet.
Ruff added, "The energy would be very low; the organisms' generation times would be very long. Understanding deep life on Earth could be a model for discovering if there was life on Mars, and if it has survived."
Subsurface marine environments were found to be particularly ubiquitous with microbial life. In these realms, Archaea—microorganisms similar to, but evolutionarily distinct from, bacteria—thrive.
Archaea are ancient forms of life, known to endure in some of the most extreme environments on the planet, such as the boiling thermal pools of Yellowstone National Park.
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Reference
S. Emil Ruff et al. (2024) A Global Comparison of Surface and Subsurface Microbiomes Reveals Large-Scale Biodiversity Gradients and a Marine-Terrestrial Divide. Science Advances, DOI: 10.1126/sciadv.adq0645
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