NASA's Mars Rover Finds New Organic Compounds Hinting at Ancient Life

NASA’s Curiosity rover has uncovered an array of organic molecules within the Gale Crater on Mars using the onboard Sample Analysis at Mars (SAM) suite. While organic compounds have been detected on Mars previously, this particular discovery was the first time a new chemical experiment was used for detection on another planet.

The discovery, detailed in the Nature journal, centers on how Curiosity's SAM module utilized tetramethylammonium hydroxide (TMAH) to identify nitrogen and sulfur-bearing molecules, similar to materials that sparked life on Earth.

The team, led by Amy Williams, associate professor in the Department of Geological Sciences at the University of Florida, are cautious, on the origins of these organic molecules. Williams and her team noted in the paper, "We are now poised to address the source of these organics, whether exogenous (e.g., meteoritic, cometary, or interplanetary dust particles) or endogenous (e.g., abiotically or biologically produced)."

Still, the detection of sulfur-rich organics is particularly notable, as sulfur can facilitate the preservation of organic matter over geological timescales, acting as a chemical "anchor" that protects the carbon chains from degradation.

Another intriguing aspect of the find is the discovery of macromolecules that share similarities with kerogen found on Earth, an organic chemical compound mixture that make up a portion of the organic matter in sedimentary rocks. On our planet, kerogen is often a byproduct of biological decay, but yet similar structures can be synthesized through non-biological reactions involving volcanic minerals and carbon dioxide. 

The findings also highlight a persistent challenge in Martian exploration, i.e. the perchlorate quandary. After all, Martian soil is rich in perchlorates, volatile salts that can destroy organic molecules when heated during the rover’s analysis process. So the fact that these complex nitrogen compounds were detected at all seems to imply that they were originally present in much higher concentrations than the data currently shows.

In a way, this chemical puzzle places the (possibly, maybe) upcoming 2033 Mars Sample Return mission in a new light. While rovers like Curiosity and Perseverance provide invaluable in situ data, the limitations of miniaturized laboratories mean that a definitive answer regarding Martian life may require the help of Earth-based facilities.