NASA's Curiosity rover has discovered some of the largest organic molecules ever found on Mars, and scientists say ordinary geological processes may not fully explain their presence. A new scientific study suggests that known abiotic processes may not be enough to explain the amount of organic material found in Martian rock samples by the Curiosity rover. Organic compounds are molecules built around carbon atoms, and on Earth, carbon-based chemical reactions form the basis of life, although some organic molecules can also be created through non-living chemical reactions.
Curiosity, which has been exploring Gale Crater since 2012, carries a compact chemistry laboratory called SAM, short for Sample Analysis at Mars. The instrument heats drilled rock powder and studies the gases released, allowing scientists to identify different molecules trapped inside.
In March 2025, researchers announced that they had detected small amounts of decane, undecane, and dodecane in rock samples analyzed by the rover. These hydrocarbons, composed only of carbon and hydrogen, are the largest organic molecules ever found on Mars. Scientists believe these compounds may be fragments of fatty acids preserved in the ancient mudstone of Gale Crater. The mudstone is formed from fine-grained sediment that was once deposited in water, suggesting that lakes may have existed in the area billions of years ago. On Earth, fatty acids are important components of cell membranes and are most commonly produced by living organisms, although certain geological processes can also produce similar molecules under the right conditions.
Curiosity's instruments can detect and measure molecules, but they cannot determine whether they were created by life. Because of this limitation, the researchers initiated a follow-up study to examine whether abiotic sources could explain the findings. One possibility is that meteorites transported organic compounds to the Martian surface. Meteorites are known to contain carbon-rich material, and Mars has experienced frequent impacts throughout its history. The scientists evaluated whether this external transport method, along with other non-biological chemical reactions, could explain the measured levels of organic compounds in the rocks.
In an article published February 4 in the journal Astrobiology, the team reports that the abiotic sources they analyzed cannot fully explain the observed abundance of organic matter. Based on these results, they say it is reasonable to consider the hypothesis that organisms may be involved in the production of these molecules.
To better understand how much organic material might have been present initially, the researchers combined laboratory radiation experiments with computer simulations and data from Curiosity. Mars lacks Earth's thick atmosphere and global magnetic field, exposing its surface to cosmic radiation. Over time, this radiation gradually breaks down complex molecules. The research team attempted to "wind back" the clock to about 80 million years, which is the estimated length of time the rock has been exposed on the Martian surface. By simulating how radiation destroys organic compounds during this time, they estimated how much material was present before degradation occurred. Their calculations suggest that the original amount may have far exceeded what can be produced by known standard abiotic processes.
The researchers caution that more research is needed before determining how quickly organic molecules decay in Mars-like rocks and Martian-like environmental conditions. Better laboratory simulations will help refine these estimates. Currently, these findings do not confirm that life once existed on Mars. Instead, they highlight that the story of the chemistry preserved in Martian rocks may be more complex than previously understood, and that non-living explanations alone may not fully solve the mystery.