For the first time, scientists have identified organic molecules containing up to 12 carbon atoms on Mars, significantly advancing our understanding of the Red Planet's potential to harbor life. The groundbreaking discovery, published on Monday, March 24, 2025, in the journal PNAS, was made using a rock sample collected by NASA's Curiosity rover in the Gale crater.
According to Caroline Freissinet, a geochemist at the Atmospheres, Environments, Space Observations Laboratory (LATMOS/CNRS) and lead author of the study, the discovered molecules, which include decane, undecane, and dodecane, represent the largest organic molecules found to date on Mars. Freissinet explained that previous organic findings consisted mainly of smaller, more stable ring-shaped molecules, while the newly discovered linear chains are fragile and susceptible to radiation damage.
The implications of finding such fragile molecules within a rock dating back 3.7 billion years are profound. Freissinet stated, "We now know that if life existed on Mars 3.5 to 4 billion years ago, its chemical residues, which are complex molecules, might have been preserved until now." The discovery fosters hope, as larger molecules suggest a system characterized by biological potential.
This research was facilitated by an innovative analytical method. The rock sample was drilled in 2013 from a site called Cumberland, but the results of this recent analysis only emerged after the development of a technique that involved preheating the sample to 450 degrees Celsius to release oxygen, followed by heating to 850 degrees for analysis. The process prevented oxidation, which typically destroys organic material during heating.
Initially, no unusual patterns were noticed in the measured data, but upon reevaluating the findings years later, Freissinet discovered anomalies in the spectrum. Collaborations with the NASA Goddard research center confirmed the presence of long-chain alkanes. Freissinet noted, "Our main hypothesis is that these molecules originate from carboxylic acids, or fatty acids, present in Martian soil. When we heat these acids to high temperatures, we break the carboxylic bond and form alkanes.”
Understanding the origin of these organic compounds enhances discussions about Mars's ancient environment. A significant factor is that the Gale crater was once a freshwater lake with neutral pH and low salinity—ideal conditions for the emergence of life. Freissinet posed an intriguing question: “If similar conditions led to the appearance of life on Earth, why not on Mars?”
Prospects for Future Exploration
The implications of this discovery are monumental, bearing significance for future exploration missions. In the short term, there’s still another sample from Cumberland that remains unexamined. Freissinet hopes to broaden the range of these organic compounds, aiming to identify alkanes with 6, 7, 8, or 9 carbon atoms that the current protocol may not be optimized to detect.
On a broader scale, the European ExoMars mission, slated for 2028, aims to explore Oxia Planum, an even older Martian site. This mission will leverage advanced instruments, including MOMA, which will enhance our understanding of whether the organic molecules are biologically or chemically derived.
The long-term aspirations of Mars exploration involve the Mars Sample Return program, projected for the late 2030s, which could facilitate the return of Martian samples collected by the Perseverance rover to Earth. This would allow for sophisticated analyses that could uncover more secrets of the Martian soil.
Freissinet concluded, “We stand keenly at the threshold of exceptional discoveries on Mars. The sample from Cumberland is one of the most precious from current space missions. If we can establish that larger molecules with an even number of carbon atoms exist, we may glean further insights into their origins and potential connections to biological activity.”
