NASA’s Curiosity rover has found the most diverse collection of organic molecules ever identified on Mars, after drilling and analyzing a rock sample in 2020 that contained 21 carbon-containing molecules. Seven of those molecules were detected for the first time on the planet, NASA said Tuesday in findings published in Nature Communications.
The sample, nicknamed Mary Anning 3, came from a part of Mount Sharp that was once covered by lakes and streams billions of years ago. That ancient terrain went through repeated surges and dry periods, and its clay minerals are especially good at preserving organic compounds. Among the newly identified molecules was a nitrogen heterocycle, a class of compound that has never before been found on the Martian surface or confirmed in Martian meteorites. Benzothiophene was another new find.
For Amy Williams, the detection matters because such structures can serve as chemical precursors to more complex nitrogen-bearing molecules. She said nitrogen heterorcycles have never been found before on the Martian surface or confirmed in Martian meteorites. The study does not settle the bigger question of whether the molecules were made by living things or by geology, but it does add to the evidence that Mars kept chemistry alive in places that looked dry and cold long after its lakes and streams disappeared.
The result also builds on work Curiosity reported last year, when it found the largest organic molecules ever discovered on Mars, including decane, undecane and dodecane. Both sets of findings came from the Sample Analysis at Mars instrument inside the rover’s belly, which can use high-temperature heating and wet chemistry to test samples. That makes the rover less of a scout than a lab on wheels, one that can squeeze clues from rocks that have sat under Martian radiation for billions of years.
Ashwin Vasavada said the work showed Curiosity and its team at their best, saying it took dozens of scientists and engineers to find the site, drill the sample and make the discoveries with the robot. He also said the collection of organic molecules increases the prospect that Mars offered a home for life in the ancient past. The next question is not whether the rock held chemistry, but what kind — and whether that chemistry ever crossed the line from mineral history to biology.