NASA’s Curiosity rover has drilled a Mars rock that contains the most diverse collection of organic molecules ever found on the planet, a result scientists said adds another piece to the case that ancient Mars may once have been habitable. The sample, collected in 2020 and nicknamed Mary Anning 3, came from a part of Mount Sharp that was covered by lakes and streams billions of years ago.
The rock yielded 21 carbon-containing molecules, including seven detected for the first time on Mars. One of the compounds was benzothiophene. The findings were detailed Tuesday in Nature Communications.
Amy Williams said nitrogen heterorcycles have never before been found on the Martian surface or confirmed in Martian meteorites, and she said that detection is profound because such structures can be chemical precursors to more complex nitrogen-bearing molecules. 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.
The result matters because it builds on a discovery Curiosity made 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 in Curiosity’s belly. The rover’s drill pulverizes a carefully selected rock into powder and feeds it into SAM, which can also do wet chemistry by dropping samples into a small cup of solvent. Only two of SAM’s wet chemistry cups contain tetramethylammonium hydroxide, a detail that helped shape what the instrument could identify.
Scientists said the sample was especially promising because the region was enriched with clay minerals that are good at preserving organic compounds. NASA said organic molecules can survive in rocks for billions of years despite radiation exposure. Even so, the discovery does not show whether the molecules were made by life or by geologic processes, and researchers said they have no way of knowing that from this sample alone.
Vasavada said the collection of organic molecules increases the prospect that Mars offered a home for life in the ancient past. For now, the answer is more cautious than the excitement around it: the rover has found a richer chemical record than ever before on Mars, but it has not found proof that Mars was once alive.