Curiosity Finds Most Chemically Diverse Organic Molecules on Mars, Including Seven New Compounds

NASA’s Curiosity rover has found the most chemically diverse set of organic molecules yet reported on Mars, including seven compounds never before detected there, according to a peer-reviewed study published Tuesday in Nature Communications. The findings add to evidence that ancient Martian rocks can preserve complex carbon chemistry over billions of years, though they do not show that life existed on the planet.

The results come from Curiosity’s “Mary Anning 3” rock sample, drilled in 2020 in Gale Crater. The sample came from the rover’s clay-rich Glen Torridon region, a roughly 3.5-billion-year-old environment whose minerals are considered especially good at preserving organic matter. In the new paper, led by University of Florida scientist Amy J. Williams, researchers reported more than 20 organic molecules — meaning carbon-containing compounds, not necessarily signs of biology — in the rock.

Among them were seven first-time detections on Mars: trimethylbenzene, tetramethylbenzene, methyl benzoate, dihydronaphthalene, naphthalene, benzothiophene and methylnaphthalene. The study also reported the first confirmed detection on Mars of a possible nitrogen heterocycle, with a mass spectrum the researchers said was most consistent with a dimethyl-indole. It also described the first robust confirmation of benzothiophene on Mars.

To find them, Curiosity used its Sample Analysis at Mars, or SAM, instrument suite. Researchers ran a wet-chemistry experiment using TMAH, a method designed to help free larger or tightly bound organic material from the powdered rock so it could be detected. SAM then analyzed the released compounds with evolved-gas analysis and gas chromatography-mass spectrometry. According to the paper, this was the first thermochemolysis experiment performed in situ on a planetary body.

The researchers said the molecules may be linked to macromolecular or refractory organic matter preserved in the rock. NASA also said lab tests on fragments of the Murchison meteorite produced some of the same compounds, supporting the idea that the technique can release such molecules from complex organic material.

The central caution is unchanged: Organic molecules are not evidence of life. Such compounds can form through nonbiological chemistry, arrive on Mars in meteorites or comets, or potentially represent degraded remnants of once-living material. The new study strengthens the case for preservation of ancient organics on Mars, but not for any one origin.

Curiosity has identified Martian organics before, and the rover’s discoveries in Gale Crater have already shown that the planet once hosted environments considered potentially habitable. What this paper adds is breadth. Rather than marking the first organic detection on Mars, it expands the known diversity of compounds in ancient rocks, following earlier reports of simpler and sulfur-bearing organics and a 2025 study describing long-chain alkanes in another Gale Crater sample.

“That detection is pretty profound because these structures can be chemical precursors to more complex nitrogen-bearing molecules,” Williams said in a NASA release. “Nitrogen heterorcycles have never been found before on the Martian surface or confirmed in Martian meteorites.”

NASA said SAM carried only two TMAH cups for this kind of experiment. The Mary Anning 3 analysis was the first use; the second cup has since been used at another site, and those results are still being analyzed.