Jun 2, 2026 08:56 PM
https://www.quantamagazine.org/the-dirt-...-20260601/
EXCERPTS: : For 15 years, Sébastien Fontaine has been trying to kill dirt. The biochemist, who runs a lab at the French National Institute for Agriculture, Food, and Environment, wanted to know how much carbon is released by soil — just dirt alone, completely devoid of life. His team sealed dirt into jars and blasted them with sterilizing gamma radiation. Then they waited for the carbon dioxide released by the soil — a sign of ongoing microbial respiration — to drop.
They waited, and waited, and waited some more: weeks, then months. Under a microscope, the irradiated soil showed no signs of life, but it continued to emit carbon dioxide. The soil wouldn’t stop breathing.
Fontaine’s lab repeated the experiments and produced the same results. Finally, convinced that they weren’t dealing with an artifact of the experimental setup, they set out to find the source of breath in dead soil.
Now, Fontaine and his colleagues have reported that their soil samples continued to consume oxygen and spew carbon dioxide(opens a new tab) for six years. In a 2025 paper in Science Advances, they proposed that a metabolic process that powers much of life is also possible outside living cells. Their experiments point to how it could work in dirt, absent the living proteins that would typically organize it. If they’re right, some biochemical reactions, such as those that release the energy of carbon-rich sugar molecules, may not be unique to living things. Such reactions — known as metabolism when performed by cells — could even predate life on Earth, Fontaine said.
The experiments show “what happens to biomolecules when they’re left to their own devices,” said Joseph Moran(opens a new tab), an organic chemist at the University of Ottawa who was not involved with the research. They’re finding that the chemistry of life is not exclusive to life, he added. “It’s the chemistry of geology.”
[...] For Joshua Schimel, a soil ecologist at the University of California, Santa Barbara, Fontaine’s findings were not too surprising. “Glucose naturally, in the process of being oxidized, is going to form some of these Krebs-cycle intermediates,” he said. Many soils are rich in iron oxides and aluminum oxides, which can catalyze this conversion, he added. The idea that metals can catalyze biochemical reactions is central to a theory about the origins of life that has emerged over the last decade...
[...] Another explanation for the observed results could be that enzymes, loosed from the irradiated cells, might be hanging around in the soil and continuing their biochemical jobs. Even when degraded, enzymes have stable backbones that might be capable of catalyzing reactions, said Sudha Rajamani(opens a new tab), an astrobiologist at the Indian Institute of Science Education and Research, Pune who wasn’t involved in the study.
Ralser agrees with her. “My gut feeling is they still have a lot of enzymes there [in Fontaine’s irradiated soil], even after six years,” he said. To know whether metals and minerals in soil could spontaneously carry out these reactions, the researchers would have to eliminate enzymes from the mixture. But that’s really hard: They would have to get the soil so hot that it would damage the soil structure itself.
However, the activity of such enzymes diminishes “exponentially” after they spill out of cells, Bouquet said. Plus, no enzyme is known to last six years, Fontaine added. He doesn’t doubt that enzymes released by living and recently dead cells contribute to carbon emissions in real-world soils, but the long-term experimental results make it “very unlikely that the respiration we observed is due to enzymes,” he said... (MORE - missing details)
EXCERPTS: : For 15 years, Sébastien Fontaine has been trying to kill dirt. The biochemist, who runs a lab at the French National Institute for Agriculture, Food, and Environment, wanted to know how much carbon is released by soil — just dirt alone, completely devoid of life. His team sealed dirt into jars and blasted them with sterilizing gamma radiation. Then they waited for the carbon dioxide released by the soil — a sign of ongoing microbial respiration — to drop.
They waited, and waited, and waited some more: weeks, then months. Under a microscope, the irradiated soil showed no signs of life, but it continued to emit carbon dioxide. The soil wouldn’t stop breathing.
Fontaine’s lab repeated the experiments and produced the same results. Finally, convinced that they weren’t dealing with an artifact of the experimental setup, they set out to find the source of breath in dead soil.
Now, Fontaine and his colleagues have reported that their soil samples continued to consume oxygen and spew carbon dioxide(opens a new tab) for six years. In a 2025 paper in Science Advances, they proposed that a metabolic process that powers much of life is also possible outside living cells. Their experiments point to how it could work in dirt, absent the living proteins that would typically organize it. If they’re right, some biochemical reactions, such as those that release the energy of carbon-rich sugar molecules, may not be unique to living things. Such reactions — known as metabolism when performed by cells — could even predate life on Earth, Fontaine said.
The experiments show “what happens to biomolecules when they’re left to their own devices,” said Joseph Moran(opens a new tab), an organic chemist at the University of Ottawa who was not involved with the research. They’re finding that the chemistry of life is not exclusive to life, he added. “It’s the chemistry of geology.”
[...] For Joshua Schimel, a soil ecologist at the University of California, Santa Barbara, Fontaine’s findings were not too surprising. “Glucose naturally, in the process of being oxidized, is going to form some of these Krebs-cycle intermediates,” he said. Many soils are rich in iron oxides and aluminum oxides, which can catalyze this conversion, he added. The idea that metals can catalyze biochemical reactions is central to a theory about the origins of life that has emerged over the last decade...
[...] Another explanation for the observed results could be that enzymes, loosed from the irradiated cells, might be hanging around in the soil and continuing their biochemical jobs. Even when degraded, enzymes have stable backbones that might be capable of catalyzing reactions, said Sudha Rajamani(opens a new tab), an astrobiologist at the Indian Institute of Science Education and Research, Pune who wasn’t involved in the study.
Ralser agrees with her. “My gut feeling is they still have a lot of enzymes there [in Fontaine’s irradiated soil], even after six years,” he said. To know whether metals and minerals in soil could spontaneously carry out these reactions, the researchers would have to eliminate enzymes from the mixture. But that’s really hard: They would have to get the soil so hot that it would damage the soil structure itself.
However, the activity of such enzymes diminishes “exponentially” after they spill out of cells, Bouquet said. Plus, no enzyme is known to last six years, Fontaine added. He doesn’t doubt that enzymes released by living and recently dead cells contribute to carbon emissions in real-world soils, but the long-term experimental results make it “very unlikely that the respiration we observed is due to enzymes,” he said... (MORE - missing details)