NASA’s Curiosity rover has detected seven organic compounds in ancient rock near Mars’s equator — five of them not previously observed on the planet. The discovery, reported in Nature Communications, also points to a separate nitrogen-bearing molecule whose structure resembles precursors to DNA, though researchers say the origin of these organics remains uncertain.
The samples came from the Glen Torridon region inside Gale Crater, a broad basin believed to have formed by an impact and to have once hosted a lake. Clay-rich sediments there preserve organic material better than many other minerals, which is why Curiosity targeted the site. The rover collected the rock samples in 2020; researchers estimate the rocks are at least 3.5 billion years old, dating to a time when Mars was warmer and wetter and potentially hospitable to life.
To analyze the samples, Curiosity used a chemical called tetramethylammonium hydroxide (TMAH) to break apart any macromolecular organics and reveal their components — a procedure that had not been performed on another planet before. The team identified seven distinct organic compounds, including benzothiophene, a molecule also found in meteorites and asteroids. That commonality supports the idea that material delivered by meteorites to early Earth and Mars could have contributed the raw ingredients for prebiotic chemistry.
Researchers caution that the detected organics can form through nonbiological processes as well as biological ones. In other words, while these molecules are carbon-based and related to the building blocks of life on Earth, their presence alone does not prove past life on Mars. The study’s lead author, astrobiologist Amy Williams, emphasized that the results strengthen evidence that Mars was a habitable world around the time life arose on Earth, but do not constitute evidence of life itself.
This finding builds on earlier Curiosity results, such as the detection in 2022 of a high ratio of carbon-12 in the same crater — a possible indicator of organic processes — and complements Perseverance’s ongoing work searching for biosignatures in Jezero Crater. The new results show that complex organic chemistry has been preserved in Martian rocks for billions of years and that current rover instruments, combined with careful site selection, can recover and analyze these ancient molecules.
The team remains cautious about interpreting the origin of the organics. They could have been generated by geologic reactions, delivered to Mars from space, or, less likely but still possible, connected to past life. Still, the study demonstrates that Mars retains a record of prebiotic chemistry and that forthcoming missions and instruments should be capable of distinguishing between different formation pathways for organic matter preserved on the planet.