AI Uncovers Oldest-Ever Molecular Evidence of Photosynthesis

"While much of the history of life on Earth is written, the opening chapters are murky at best. On our ever-changing world, the older a rock is, the more it has changed, obscuring or even erasing evidence of ancient life. Beyond a hazy boundary of circa two billion years, in fact, this interference is so total that no pristine, unaltered Earth rocks are known to exist, making any potential sign of biology as clear as mud. At least until now."

"At least until now. In a study published on November 17 in the Proceedings of the National Academy of Sciences, a group of researchers say they've leveraged artificial intelligence to follow life's trail further back in time than ever before, using machine learning to distinguish the echoes of biology from mere abiotic organic molecules in rocks as old as 3.3 billion years."

"The study also flags signs of photosynthesis in 2.5-billion-year-old rockssome 800 million years earlier than any other confirmed biomolecular evidence. The authors suggest that in the not-too-distant future similar techniques may be used to seek signs of alien life on Mars or the icy ocean moons of the outer solar system. And such astrobiological applications wouldn't necessarily demand the extremely costly task of retrieving material from Mars or any other extraterrestrial locale for in-depth study in labs back on Earth."

Machine learning can distinguish biological from abiotic organic molecules in rocks as old as 3.3 billion years. That capability more than doubles the previous limit for confident molecular detection of ancient life beyond 1.6-billion-year-old rocks. The technique identifies signatures consistent with photosynthesis in 2.5-billion-year-old rocks, pushing confirmed biomolecular evidence back by roughly 800 million years. The approach can run on planetary rovers, potentially enabling in-situ astrobiological searches without returning samples to Earth. The method separates biological echoes from abiotic organic signals in heavily altered, ancient rock materials where pristine samples are unavailable.

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