Researchers report earliest molecular proof of photosynthetic life

Using a machine studying approach that compares molecular fingerprints left behind by residing organisms, researchers have detected signs of photosynthetic life in rocks 2.5 billion years old— about 800 million years older than any beforehand confirmed proof (Proc. Natl. Acad. Sci. U.S.A. 2025, DOI: 10.1073/pnas.2514534122).

In the examine, led by Robert Hazen on the Carnegie Institution for Science, researchers analyzed 406 numerous rock and natural samples utilizing pyrolysis fuel chromatography/mass spectrometry (GC/MS), a technique that breaks down samples and measures the fragments of natural molecules they launch. Many of the bigger biomolecules serving as markers for detecting life degrade over time. But when subjected to GC-/MS, every sort of organism—from historical fungi to trendy animals—produces a definite sample of molecular fragments, says Anirudh Prabhu, one of many examine’s authors.

Pyrolysis GC/MS knowledge can be utilized to infer a pattern’s origin, however recognizing tiny variations throughout lots of of samples is difficult and time consuming. To assist, the researchers utilized a machine studying mannequin that compares the molecular patterns related to numerous fossil varieties. Instead of zeroing in on particular person molecules, the system scans the total chemical panorama, detecting faint signatures even in degraded samples.

“It’s basically analogous to facial recognition, except instead of facial features, it’s looking at these chemical datasets,” says Michael Wong, additionally one of many examine’s authors.

The mannequin distinguishes organic from nonbiological supplies with greater than 90% accuracy. It additionally determines a pattern’s origins—for instance, if it got here from a meteorite or originated on Earth.

After confirming that the approach reliably identifies samples with identified origins, the researchers put it to work on unknown ones. It discovered indicators of life in rocks round 3.3 billion years previous and indicators of photosynthetic organisms in samples 2.5 billion years previous.

“We roughly double the age in which we can use suites of organic molecules to identify signs of life in ancient rocks,” Wong says.

The mannequin isn’t excellent, although. It struggled when the workforce had solely a small variety of samples to coach on. The researchers say that increasing their dataset ought to assist, they usually’ve put out a name for others to ship their samples, hoping to recover from 1,000 complete for evaluation.

The workforce additionally notes that some intently associated specimens are significantly laborious to inform aside. For occasion, distinguishing between photosynthetic and nonphotosynthetic plant materials is difficult as a result of their chemical profiles are so related. Accuracy in these instances dropped to round 79%, Prabhu says.

“I think what’s so valuable about this project is it’s telling the research community where we need more information,” says Linda Kah, a professor of carbonate sedimentology and geochemistry on the University of Tennessee, Knoxville, who was not concerned within the examine. Although Kah agrees that the mannequin will profit from extra numerous samples to scale back any potential biases, she says the large knowledge method is a “magnificent effort.”

The researchers hope to develop the instrument to be used in planetary exploration. Some robotic missions—together with NASA’s Curiosity rover on Mars—already carry pyrolysis GC/mass spectrometers, and sometime a machine studying methodology like this one may permit spacecraft to research and interpret knowledge on their very own, Wong says. Because the mannequin seems on the complete chemical panorama quite than focusing on identified biomolecules, it could even detect completely alien types of life, he provides.