A NASA team has identified previously undetected organic molecules in a Martian surface sample collected by the Curiosity rover in 2017. The findings, published in the journal Nature, mark a significant advancement in Mars exploration.
The Curiosity rover's Sample Analysis at Mars (SAM) instrument, equipped for wet chemistry experiments, enables gas chromatography-mass spectrometry analysis of polar molecules like amino acids and carboxylic acids.
In a recent study, researchers analyzed samples from the "Bagnold Dunes" collected in 2017. While no amino acid derivatives were found, the team successfully isolated benzoic acid and ammonia—compounds that could hint at ancient life, detected for the first time on Mars.
This breakthrough is promising but not conclusive proof of past life. The study notes these molecules could also arise from geological processes. Still, it's a major step forward.
"This experiment is a clear success," says lead author Maëva Millan from NASA's Goddard Space Flight Center. "Even without finding biosignatures, we've proven this technique's potential."
Curiosity has previously detected organics in Martian soil; this discovery expands that inventory.
In March 2020, Curiosity identified thiophenes—organic compounds containing four carbon and one sulfur atom. On Earth, they appear in kerogen, coal, crude oil, stromatolites, microfossils, and even white truffles.
Thiophenes can form via sulfate reduction in two ways.
One abiotic pathway involves heating precursors to 120°C, possible during meteorite impacts on Mars.
The other requires bacteria, feasible in Mars' ancient environment over three billion years ago, when a thicker atmosphere supported warmer temperatures and surface liquid water.
Like benzoic acid and ammonia, thiophenes may have biological or non-biological origins. Future missions, including the differently equipped Perseverance rover, may provide clarity.
