Scientists have found surprising amounts of bacteria living on clay-rich rocks below the Pacific sea floor. The discovery raises the possibility of equally resistant microbes living deep within the surface of Mars.
Ancient volcanic rocks below the sea bottom of the Pacific Ocean provide a habitat for dense groups of microbial communities, according to a new study published in Communications Biology. The microbes were found at depths of up to 100 meters below the seafloor, huddled within the crevices of ancient clay-rich volcanic rocks.
“Life will find a home in virtually every available crevice,” said Jennifer Biddle, an associate professor at the University of Delaware in the United States who was not involved in the new research, in a phone conversation with Gizmodo. “Previous studies of the past 20 years have hinted at this possibility, that many microbes may exist within the cracks or crevices of ocean crusts, but this new study is good because it is actually the first evidence of active microbes within these rocks. in particular, and not only its fossilized remains ”.
Underground microbes have already been found in the past. In 2006, for example, scientists they detected bacteria about 3 kilometers below the Earth’s surface, and in 2018, researchers They found Photosynthetic bacteria hundreds of meters below the surface of an abandoned mine in Spain. At the end of March of the same year, a study describing microbial communities that live about 792 meters below the sea floor.
What makes the new discovery special is that the microbes were alive and mined from ancient volcanic rocks aged between 13.5 and 104 million years. Whether active microorganisms could be found in these rocks was an important and unanswered question when starting this research, and now the new study suggests that they live and thrive in their extreme habitat.
Lead author Yohey Suzuki of the University of Tokyo in Japan collected the samples in 2010. The researchers selected three different points at the bottom of the Pacific Ocean between Tahiti and New Zealand. To rule out polluting sources, the scientists selected areas away from the hydrothermal vents.
A 5.7-kilometer-long metal tube was lowered to the ocean floor, and a drill dug an additional 125 meters into the seafloor. During the first 75 meters of the journey, the drill made its way through thick mud, followed by another 40 meters through solid rock.
Once in the lab, the samples revealed traces of the bacteria within the cracks in the volcanic rock. These small fractures, less than 1 millimeter wide, formed when the hot lava was cooling.
Suzuki found the bacteria in surprising densities, with colonies reaching 10 billion bacterial cells for every cubic centimeter, which is about the same amount found in the human gut. The seabed itself has barely 100 cells per cubic centimeter.
“Now I’m basically hoping that I can find life on Mars. If not, it must be that life is based on some other process that Mars does not have. ”
The bacteria is likely attracted to clay-rich minerals, which provide a suitable habitat for aerobic microbes that feed on oxygen and organic nutrients. And as Biddle said to Gizmodo“The clay has a charged surface, which makes it easier for bacteria to adhere.” Using DNA analysis, the researchers identified distinct but similar aerobic bacterial species extracted from the different locations they analyzed.
“This discovery of life where no one expected it, on solid rock below the sea floor, could be changing the game for the search for life in space,” said Suzuki in a press release. “Now I’m basically hoping that I can find life on Mars. If not, it must be that life depends on some other process that Mars does not have, as perhaps in tectonic plates, “he added.
Suzuki and his colleagues will soon collaborate with NASA as they work on a plan to return Martian rocks to Earth for analysis. The rover Perseverance, which will launch into space later this summer (let’s cross our fingers), is explicitly designed for this purpose. The rover will collect materials and deposit them on the Martian surface for a future sample return mission.
Suzuki says that the clay minerals below the Pacific seafloor could be similar to minerals on Mars.
“The minerals are like a fingerprint of the conditions that were present when the clay formed,” he said. “Neutral to slightly alkaline levels, low temperature, moderate salinity, iron-rich environment, basaltic rock – all of these conditions are shared between the deep ocean and the surface of Mars.”
Biddle, however, was cautious about the astrobiological implications of the new study.
“Can life be more robust? Sure, but I would be cautious with this type of interpretation, “he told Gizmodo. “Mars may be missing a complete biogeochemical cycle for all the elements required for life,” he explained, adding that the new study “is not a definitive thing” to demonstrate that life is certain to exist elsewhere in the solar system. “Other things must be present to allow life to survive,” he said.
With a pending Mars sample return mission in development, we could soon test this theory. That being said, we probably won’t have satisfactory answers until we can dig deep into the Martian crust, which the Perseverance rover won’t be able to do. So for now, we will have to be content with these fascinating speculations.