In July, scientists discovered a rock that “corrected” the date of the origin of complex life, revealing that they were off by about 1.5 billion years. In that case, experts found evidence of environmental conditions suitable for animal life in sediments deposited around 2.1 billion years ago in the Franceville Basin of Gabon. Recently, another group of researchers uncovered the oldest life form in similar conditions.
The research. In the study published in Microbial Ecology, a team from the University of Tokyo’s Department of Earth and Planetary Sciences discovered that a rock fracture, sealed nearly 50 feet underground, has harbored microbes for the past 2 billion years.
The nearly 12-inch sample, excavated from beneath South Africa’s Bushveld Igneous Complex, is up to 1.9 billion years older than previous microbial record holders. This finding could help researchers understand the early stages of evolutionary life on Earth and beyond.
Rewriting antiquity. Lead author Yohey Suzuki explained in a press release that, until now, scientists didn’t know if 2-billion-year-old rocks were habitable: “We didn’t know if 2-billion-year-old rocks were habitable. 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.”
As the researcher noted, these types of discoveries are critical because studying the DNA and genomes of these ancient microbes could provide insights into the evolution of early life on Earth.
The “home” of the microbes. Scientists found these microbes inside a sealed fracture in ancient rock, an “intrusion” that formed as magma slowly cooled beneath the Earth’s surface. The site where this process occurred, the Bushveld Igneous Complex, isn’t just any place. It covers a vast area and contains some of the world’s richest ore deposits, including about 70% of the world’s mined platinum.
Since its formation, the site’s relatively unchanged state has provided the perfect conditions for ancient microbial life to survive.
The life of a microbe. The key to how life can exist on Earth for billions of years lies in the slowness of all processes. Living far below the Earth’s surface, these organisms evolve incredibly slowly and have a very slow metabolic rate. The study has revealed that they can persist in igneous rocks on geological time scales of at least 2 billion years.
The finding. To obtain the sample, the researchers drilled nearly 50 feet underground to retrieve a 12-inch piece of rock core. An analysis revealed living microbial cells tightly packed within the rock fractures, isolated from the outside environment by clay-filled voids.
The next step was to confirm that the organisms were indeed “native” to the rock. To do this, the team stained the microbes’ DNA and used infrared spectroscopy to examine the proteins they contained and those found in the surrounding clay. Their work confirmed that the organisms were alive, uncontaminated, and had been there for at least 2 billion years.
From Earth to Mars. According to the researchers, these are the oldest living microbes ever found in rock samples, with implications that extend beyond Earth. The team hopes their discoveries could aid the search for evidence of life on Mars.
“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,” Suzuki concluded.
Image | Y. Suzuki, S. J. Webb, M. Kouduka et al. 2024/ Microbial Ecology
View 0 comments