Researchers have discovered living microbes inside a sealed crack within 2-billion-year-old rock. This rock was sourced from the Bushveld Igneous Complex in South Africa, a region known for its abundant mineral resources. This finding marks the oldest known presence of living microbes within ancient rock. The research team enhanced their methodology by utilizing three imaging techniques—infrared spectroscopy, electron microscopy, and fluorescent microscopy—to verify that these microbes originated from the rock sample itself and were not introduced through contamination during the extraction and examination process. Studying these microbes could provide insights into the early evolution of life on Earth, as well as inform the search for life on other planets, especially in similarly aged rock samples returned from Mars.
Buried deep within the Earth, there exist ancient yet living colonies of microbes that have adapted to thrive in rocks located far below the surface, surviving for thousands and even millions of years. These remarkable microorganisms seem to exist at a slow pace, showing minimal evolution across vast geological timescales, thus allowing us a glimpse into the distant past. Recently, scientists have found active microbes within a rock sample believed to be 2 billion years old.
“Previously, we weren’t certain whether rocks dating back 2 billion years could support life. Prior to this, the oldest geological layer where living microorganisms were discovered was around 100 million years old beneath the ocean floor, making this a groundbreaking find. By analyzing the DNA and genomes of such microbes, we may better understand the origins of early life on Earth,” stated Yohey Suzuki, the lead author and an associate professor at the University of Tokyo’s Graduate School of Science.
This particular rock sample was extracted from the Bushveld Igneous Complex (BIC), a formation in northeastern South Africa that originated from magma cooling slowly beneath the Earth’s crust. The BIC spans roughly 66,000 square kilometers (comparable to Ireland), and its thickness can reach up to 9 kilometers. It hosts some of Earth’s most valuable mineral deposits, including about 70% of globally mined platinum.
Due to its formation process and the minimal geological changes that have occurred since, the BIC is thought to offer a stable environment for ancient microbial life to persist until now.
With support from the International Continental Scientific Drilling Program—a nonprofit focused on geological exploration—the team retrieved a rock core sample measuring 30 centimeters, taken from around 15 meters below the surface. After slicing the rock into thin sections for analysis, the researchers discovered living microbial cells densely packed in the rock’s cracks. Notably, any openings around these cracks were filled with clay, preventing other organisms from infiltrating or the microbes from escaping.
The team built upon a previously developed technique to ensure that the microorganisms were truly native to the rock sample and not introduced through contamination during the drilling or analysis. They stained the microbial DNA and used infrared spectroscopy to examine the proteins in the microbes and their surrounding clay, confirming both the viability and authenticity of the microorganisms.
“I am very curious about subsurface microbes, not just on our planet but also regarding their potential existence on other celestial bodies,” said Suzuki. “Although Martian rocks tend to be significantly older (ranging from 20 to 30 billion years old), NASA’s Perseverance rover is expected to return rock samples that are of a similar age to those we studied. The discovery of microbial life in these 2 billion-year-old Earth samples, combined with our ability to confirm their authenticity, excites me about the possibilities for finding life in samples from Mars.”
