Scientists have discovered a simple and reliable test for signs of past or present life on other planets — “the holy grail of astrobiology.”
In the journal Proceedings of the National Academy of Sciences, researchers now report that, with 90% accuracy, their new artificial intelligence-based method distinguished modern and ancient biological samples from those of abiotic origin (https://www.pnas.org/doi/10.1073/pnas.2307149120).
Most immediately, the new test could reveal the history of mysterious, ancient rocks on Earth, and possibly that of samples already collected by the Mars Curiosity rover’s Sample Analysis at Mars (SAM) instrument. The latter tests could be conducted using an onboard analytical instrument nicknamed “SAM” (for Sample Analysis at Mars.
“We’ll need to tweak our method to match SAM’s protocols, but it’s possible that we already have data in hand to determine if there are molecules on Mars from an organic Martian biosphere.”
“The search for extraterrestrial life remains one of the most tantalizing endeavors in modern science,” says lead author Jim Cleaves of the Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC.
“The implications of this new research are many, but there are three big takeaways: 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.”
The innovative analytical method does not rely simply on identifying a specific molecule or group of compounds in a sample. Instead, the researchers demonstrated that AI can differentiate biotic from abiotic samples by detecting subtle differences within a sample’s molecular patterns as revealed by pyrolysis gas chromatography analysis (which separates and identifies a sample’s component parts), followed by mass spectrometry (which determines the molecular weights of those components).
Vast multidimensional data from the molecular analyses of 134 known abiotic or biotic carbon-rich samples were used to train AI to predict a new sample’s origin. With approximately 90% accuracy, AI successfully identified samples that had originated from:
• Living things, such as modern shells, teeth, bones, insects, leaves, rice, human hair, and cells preserved in fine-grained rock
• Remnants of ancient life altered by geological processing (e.g. coal, oil, amber, and carbon-rich fossils), or
• Samples with abiotic origins, such as pure laboratory chemicals (e.g., amino acids) and carbon-rich meteorites.
The authors add that until now the origins of many ancient carbon-bearing samples have been difficult to determine because collections of organic molecules, whether biotic or abiotic, tend to degrade over time.
Surprisingly, in spite of significant decay and alteration, the new analytical method detected signs of biology preserved in some instances over hundreds of millions of years.
AR #80
The Case for Life on Mars Gets Stronger
