Is there life on Mars? Or was there in its past? What about other planets?
US scientists believe an artificial intelligence algorithm may be able to provide a reliable test to answer these questions – considered the “Holy Grail of Astrobiology.”
The AI method developed at the Earth and Planets Laboratory at the US Carnegie Institution for Science can identify with 90% accuracy both present and ancient biological samples from those of inorganic origin.
The findings are detailed in a paper published in the Proceedings of the National Academy of Sciences.
Search for life – on Earth as well
“This routine analytical method has the potential to revolutionise the search for extraterrestrial life and deepen our understanding of both the origin and chemistry of the earliest life on Earth,” says research leader Dr Robert Hazen. “It opens the way to using smart sensors on robotic spacecraft, landers and rovers to search for signs of life before the samples return to Earth.”
It could also be used closer to home to analyse ancient rocks on Earth to determine if they contain signs of prehistoric life.
The technique could resolve mysteries such as including the origin of 3.5-billion-year-old black sediments from Western Australia. The samples are the subject of scientific debate with some researchers believing the sediments contain Earth’s oldest fossil microbes, while others claim they are inorganic.l
Lead author Jim Cleaves says there are three big takeaways of the research: “First, at some deep level, biochemistry differs from abiotic organic chemistry; second, we can look at Mars and ancient Earth samples to tell if they were once alive; and third, it is likely this new method could distinguish alternative biospheres from those of Earth, with significant implications for future astrobiology missions.”
A new method
The AI doesn’t just focus on a single molecule or group of compounds to determine whether there are signs of life. It uses pyrolysis gas chromatography and mass spectroscopy to detect subtle differences within a sample’s molecular patterns.
Tested on 134 known organic and inorganic samples from Earth, the machine learning tool was able to correctly identify the origin approximately 90% of the time.
It was able to determine living things such as shells, teeth, bones, leaves, rice, human hair and cells in rock. It could also detect remnants of ancient life altered through long-timescale geological processes, such as coal, oil, amber and carbon-rich fossils.
The AI was also able to determine when samples such as pure laboratory chemicals like amino acids were produced in abiotically.
Extraterrestrials can no longer hide
The team believe their tool will even be able to find life on other worlds where the organic chemistry is unlike on Earth.
“We began with the idea that the chemistry of life differs fundamentally from that of the inanimate world; that there are ‘chemical rules of life’ that influence the diversity and distribution of biomolecules. If we could deduce those rules, we can use them to guide our efforts to model life’s origins or to detect subtle signs of life on other worlds,” says Hazen.
“These results mean that we may be able to find a lifeform from another planet, another biosphere, even if it is very different from the life we know on Earth. And, if we do find signs of life elsewhere, we can tell if life on Earth and other planets derived from a common or different origin.”
The researchers are particularly buoyed by the tool’s ability to not only distinguish between biotic and abiotic samples. It can tell apart abiotic, living biotic and fossil biotics.