Today, the Curiosity rover roaming Mars is met with a dusty, lifeless world. But there’s evidence that the planet was once awash with liquid water. Could Mars have supported life?
In a quest to answer the question of habitability, scientists equipped Curiosity with a suite of instruments and milliliter-scale sealed cups containing liquid reagents in order to perform nine wet chemistry experiments.
Searching for organics in 2020, the rover drilled a bit of clay from the Martian surface, opened a cup, and performed the first off-Earth thermochemolysis experiment. Now researchers have identified the molecules liberated from that Martian rock (Nat. Commun. 2026, DOI: 10.1038/s41467-026-70656-0).
“We have not found evidence of life,” says astrobiologist Amy J. Williams, a professor at the University of Florida and a leader of the new work. Rather, the experiment “provides some of the most conclusive evidence that complex organic carbon is preserved in the near-surface of Mars,” she says.
The power of the experiment came from the reagent held in that tiny cup. It was one of two containing tetramethylammonium hydroxide (TMAH), a highly alkaline chemical used in thermochemolysis. When heated, TMAH hydrolyzes and methylates carbons, Williams says. This not only makes organics more volatile and thus easier to detect but also breaks large molecules into fragments that can be detected with Curiosity’s on-board gas chromatography/mass spectrometry instrument.
Using TMAH, Williams and her team were able to confirm the presence of and to identify seven aromatic organic molecules in the Martian sample, including benzothiophene and naphthalene—the first confirmation of either molecule on Mars.
Seeing benzothiophene is particularly exciting for Williams. “We know it formed very early on in the formation of the solar system,” she says. After the planets formed, they were likely bombarded with meteorites rich in the sulfur heterocycle. Its presence in this sample suggests that large organics could be preserved within Martian bedrock for billions of years.
The scientists also saw signals for an additional 16 molecules but were unable to characterize them beyond their shared functional groups and other structural similarities. One of the molecules is clearly a nitrogen heterocycle similar to an indole, Williams says.
“Indoles are one of the many precursors that probably play a role in forming RNA and DNA,” Williams says. Scientists have never found nitrogen heterocycles on Mars. Detecting this one “gives me a lot of hope for the past habitability of Mars,” she adds.
Williams sees this work as trailblazing for the next set of out-of-this-world TMAH thermochemolysis experiments. In 2028, the European Space Agency, in collaboration with NASA, plans to launch a Mars rover—the Rosalind Franklin—carrying its own instrument suite and TMAH experiments. The Dragonfly mission will take off the same year bound for Titan, Saturn’s largest moon. After it arrives, it will deploy a drone-like rotorcraft equipped with a motorized lab similar to the one on Curiosity.
“This work is extremely exciting to me,” says planetary scientist Melissa Trainer, one of the leaders of the Dragonfly mission. “This is the first time that the TMAH reagent has been used on another planet.” It’s proof that an automated system can do the experiment and makes her more confident in the success of the Dragonfly mission.
“It just shows the power of what we can do with these instruments,” Trainer says. “The more planets and planetary bodies we can go to and make similar measurements, the more we’re going to understand in the search for life.”
2026 American Chemical Society
