Living microbes have been found sealed within the fracture of a 2-billion-year-old rock dug up from the Bushveld Igneous Complex in South Africa.
The remarkable discovery is the oldest known example of living microorganisms found within ancient rock.
Scientists say the find helps us understand very early life on Earth, and could even be used in the search for extraterrestrial life on Mars.
The research, led by Yohey Suzuki, an associate professor from the Graduate School of Science at the University of Tokyo, was published in Microbial Ecology.
Microbial time capsules
The Bushveld Igneous Complex (BIC), a vast underground rock formation renowned for its rich ore deposits, has long been a point of interest for geologists.
Spanning an area of 66,000 square kilometres, roughly the size of Ireland, the BIC is a colossal remnant of ancient magma that cooled and solidified beneath the Earth’s crust. Over billions of years, this formation has remained largely undisturbed, providing a stable habitat for ancient life to potentially flourish undetected – until now.
The discovery of these microbes is not just a scientific curiosity; it offers a rare opportunity to peer into Earth’s deep past. While microbial colonies have been found living in ancient environments before, such as in 100-million-year-old oceanic deposits, this discovery shatters previous records. The microbes were found sealed in tiny fractures within the rock, completely isolated from the outside world for eons.
Lead researcher Yohey Suzuki says the find opens new avenues for understanding early life on Earth.
“We didn’t know if 2-billion-year-old rocks were habitable," says Suzuki. "Until now, the oldest geological layer in which living microorganisms had been found was a 100-million-year-old deposit beneath the ocean floor, so this is a very exciting discovery.
"By studying the DNA and genomes of microbes like these, we may be able to understand the evolution of very early life on Earth.”
A glimpse into life on other planets?
One of the most exciting aspects of this discovery is its potential implications for the search for life beyond Earth.
The extreme age and isolation of these microbes have given scientists a new reference point in their hunt for life on other planets, particularly Mars. With NASA’s Mars rover Perseverance currently collecting samples of Martian rock that could be up to 3.7 billion years old, Suzuki and his team believe this new research could help guide the study of extraterrestrial samples.
“I am very interested in the existence of subsurface microbes not only on Earth, but also the potential to find them on other planets,” says Suzuki.
“NASA’s Mars rover Perseverance is currently due to bring back rocks that are a similar age to those we used in this study. Finding microbial life in samples from Earth from 2 billion years ago and being able to accurately confirm their authenticity makes me excited for what we might be able to now find in samples from Mars.”
How they did it
The study's success rested on the team's innovative use of advanced imaging techniques to confirm that the microbes were native to the ancient rock, not the result of contamination during drilling or analysis.
To ensure the microbes were indeed ancient, the researchers employed a combination of infrared spectroscopy, electron microscopy and fluorescent microscopy. This allowed them to observe the DNA of the microbes and analyse the proteins in the surrounding clay to confirm that the cells were not only alive but also belonged to the rock itself.
The microbial cells were found tightly packed into cracks in the rock, surrounded by clay that had sealed them in place. These cracks, clogged with clay, formed natural barriers that prevented anything from entering or leaving, creating a tiny, isolated world for the microorganisms.
A window into early evolution
This discovery has significant implications for our understanding of how life on Earth began and evolved in extreme environments. By studying the genomes of these ancient microbes, researchers hope to gain insight into the development of early life forms, which could also inform how we search for life on other planets.
The ancient microbes found in the BIC provide a fascinating glimpse into the resilience of life, showing that even in the most isolated, ancient environments, life finds a way to survive. As scientists continue to explore both the Earth and beyond, this discovery will undoubtedly fuel further research into the origins of life – and perhaps, the discovery of life on other planets.
Find our more about the study: Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa
Main image: living microbial cells in the 2-billion-year-old rock fissure/Y. Suzuki, S. J. Webb, M. Kouduka et al.
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