The search for extraterrestrial life on Mars took a major leap forward after scientists detected the longest organic molecules found on the planet to date.
Drilling into the Gale Crater Mudstone
NASA’s Curiosity rover drilled into a rock target named ‘Cumberland’ on May 19, 2013, collecting a powdered sample from the interior of a rock inside the Gale crater. This 160-kilometer-wide area once housed an ancient lake containing liquid water, mild temperatures, appropriate pH levels, and necessary energy sources. The specific type of stone in the region—mudstone containing layers of clay—effectively trapped and preserved the organic material over billions of years.
For years, researchers kept these collected samples in storage while developing new laboratory methods. Caroline Freissinet, an astrochemistry specialist and researcher at the French National Centre for Scientific Research who led the study, identified a unique spectral peak corresponding to decane. After intensive laboratory work, the team successfully extended the detection to undecane and dodecane.
Decane, Undecane, and Dodecane Discovery
The newly identified compounds are long, chain-shaped molecules known as alkanes. Specifically, the team found molecules composed of 10, 11, and 12 carbon atoms. These molecules are significantly more fragile than the ring-shaped, aromatic carbon molecules detected on Mars in previous missions.
Finding these delicate compounds in 3.7-billion-year-old rocks proves they survived geological periods without breaking down. On Earth, long-chain alkanes can originate from long-chain fatty acids, which possess the capability to assemble themselves into capsule-like vesicles on a planet’s surface. This chemical pathway mirrors how life is believed to have originated on Earth.
Unresolved Questions Regarding Biotic Origins
Despite the significance of detecting decane, undecane, and dodecane, the origin of these organic molecules remains undetermined. Organic molecules serve as building blocks for life, but they can also form independently of biological processes through chemical reactions.
Confirming whether these molecules stem from biotic or abiotic processes requires further investigation. Researchers aim to detect additional molecules from the same family, expanding the search to encompass carbon chains ranging anywhere from eight to 18 atoms. Scientists also look for a distinct statistical difference in the abundance of molecules with even and odd numbers of carbon atoms, a pattern typically observed in biological samples on Earth.
