It’s really true! Ancient microbes have been discovered alive in a 2 billion year old rock!

Wednesday 09th October 2024 02:23 AM

Microorganisms discovered in sealed rock could help us understand primitive life on Earth and the search for evidence of life on Mars (image: Yohey Suzuki et al).

In the depths of the Earth, creatures several billion years old are still alive without us knowing that they exist. It looks like a movie script, but the truth is that billions of years old colonies of microorganisms could actually be hidden in rocks beneath the surface.

These microscopic and resistant organisms seem to live at a slower pace than those on the surface, evolving very little over large geological time scales. The study of the DNA and genomes of these microbes therefore allows us to better understand the evolution of primitive life on Earth.

Microorganisms of this type have been discovered before, but a rock extracted from the Bushveld igneous complex in South Africa has had an unexpected surprise for scientists studying the geology of the site. Researchers discovered living microbes in a rock sample estimated to be 2 billion years old.

Scientists discover living things dating back two billion years ago

The rock sample was taken from the Bushveld Igneous Complex (BIC), a rock intrusion located in northeastern South Africa which formed when magma slowly cooled beneath the Earth’s surface. The BIC covers an area of approximately 66,000 km² (roughly the size of Ireland) and contains some of the richest ore deposits in the world, including approximately 70% of the platinum mined globally.

The sample was taken from the Bushveld Igneous Complex in South Africa (image: Yohey Suzuki et al.)

With the help of the International Continental Scientific Drilling Program, the team took a 30 cm long rock sample from a depth of about 15 meters. The rock was then cut into thin slices and analyzed. That’s when the team discovered living microbial cells, densely packed in some cracks in the rock. The cracks were sealed with clay, which made it impossible for organisms to exit or for other external elements to enter.

Due to its formation and little deformation or change that has occurred since, the BIC is believed to have provided a stable habitat for ancient microbial life until today.

The team used a special technique to confirm that the microbes were native to the rock and did not result from contamination during the drilling or analysis process. To do this, the scientists combined three types of images (infrared spectroscopy, electron microscopy and fluorescence microscopy) at the same time.

The team used a technique they had previously developed to confirm that the microbes originated in the rock and did not result from contamination (image: Yohey Suzuki et al).

By staining the DNA of microbial cells and using the technique to examine proteins from microbes and the surrounding clay, the researchers were able to confirm that the microorganisms were alive and not contaminants.

Until now, the oldest geological deposit in which living microorganisms had been discovered was “only” 100 million years old and was located under the ocean floor. It is therefore the oldest sample ever discovered by scientists.

Today, the study of these microbes could help us better understand the evolution of primitive life on planet Earth. This discovery is a window into the past, showing us what life was like billions of years ago.

But this discovery also raises the possibility that this same type of life exists on other planets. The Perseverance rover is currently collecting Martian rocks of a similar age to the rocks used in this study. This means that we could even soon discover Martian microorganisms.

Article reference:

Yohey Suzuki et al. Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa. Microbial Ecology, 2024; 87 (1).