The oldest living microorganisms ever found in rocks could be beneficial for scientists searching for life on other planets.
Researchers excavated a 2-billion-year-old rock in South Africa and unexpectedly discovered that it contained groups of living microorganisms that are even thriving, as reported by IFL Science on October 4. This is the oldest example of living microorganisms ever found in ancient rock.
Microbial cells in the cracks of the 2 billion-year-old rock sample, stained blue for analysis. (Photo: Y. Suzuki/SJ Webb/M. Kouduka/Microbial Ecology).
“We did not know if these 2 billion-year-old rocks were still suitable for life. Previously, the oldest geological layer where living microorganisms were found was a 100 million-year-old sediment layer at the bottom of the ocean. Therefore, this new discovery is very intriguing. By studying the DNA and genome of such microorganisms, we can understand the evolutionary process of early life forms on Earth,” said Yohey Suzuki, an expert from the University of Tokyo and the lead author of the new study published in the journal Microbial Ecology.
The microorganisms live in a sealed crack within the ancient rock, excavated from the Bushveld Igneous Complex—a massive rock formation created when magma cooled slowly beneath the Earth’s surface. This vast complex is nearly the size of Ireland and contains some of the largest ore deposits, including approximately 70% of the world’s platinum. It has remained relatively intact since its formation, providing perfect conditions for ancient microorganisms to survive. Such organisms live deep below the Earth’s surface, evolve extremely slowly, and have a very slow metabolic rate, allowing them to exist for long periods within volcanic rock—up to 2 billion years, as in this new study.
With the support of the International Continental Scientific Drilling Program (ICDP), the research team drilled down 15 meters to retrieve a 30 cm long core sample. Upon closer examination, they found living microbial cells closely packed in the cracks of the rock, separated from the outside environment by clay-filled cavities.
To confirm that the microorganisms originated from the rock sample and were not newly introduced during the drilling or examination process, the team stained their DNA. They also used infrared spectroscopy to observe the proteins inside the microorganisms and the proteins in the surrounding clay. This allowed them to determine that the microorganisms were indeed alive and not newly infiltrated.
The discovery of the oldest living microorganisms ever found in rock is highly significant. “I am very excited about the existence of microorganisms beneath the surface, not only on Earth but also the potential to find them on other planets,” Suzuki shared.
Martian rocks are often much older. “However, NASA’s Perseverance rover is preparing to bring back rocks that are similar in age to the type of rock we used in this new research. Finding living microorganisms in samples from Earth that are 2 billion years old and being able to verify them makes me very excited about what we could find in Martian samples,” Suzuki added.
