Curiosity Rover Unveils Largest Carbon Chains Yet in 3.7-Billion-Year-Old Martian Rock

The longest molecules ever found on Mars have been unearthed by NASA's Curiosity rover, and they could mean the planet is strewn with evidence for ancient life.

Molecule chains containing up to twelve carbon atoms linked together were detected in a 3.7 billion-year-old rock sample collected from a dried-up Martian lakebed named Yellowknife Bay, according to a study published March 24 in the journal Proceedings of the National Academy of Sciences .

These long carbon chains are thought to have originated from molecules called fatty acids, which, on Earth, are produced by biological activity. While fatty acids can form without biological input, which may be the case on Mars, their existence on the Red Planet means that signs of life may be lurking within its soil.

"The fact that fragile linear molecules are still present at Mars' surface 3.7 billion years after their formation allows us to make a new statement: If life ever appeared on Mars billions of years ago, at the time life appeared on the Earth, chemical traces of this ancient life could still be present today for us to detect," study co-author Caroline Freissinet An analytical chemist working at the French National Centre for Scientific Research within the Laboratory for Atmospheres and Space Observations shared insights with Live Science.

The molecules—hydrocarbon chains consisting of 10, 11, and 12 carbon atoms known as decane, undecane, and dodecane—were identified using the Sample Analysis at Mars (SAM) instrument aboard Curiosity.

No stone unturned

The Curiosity Rover landed on Mars in 2012 within the Gale Crater, which spans an impressive 96 miles (or 154 kilometers) across and was created by a past asteroid strike. Since then, the rover has journeyed approximately 20 miles (32 km) Across the crater, exploring locations such as Yellowknife Bay and Mount Sharp (Aeolis Mons), a 3.4-mile-tall (5.5 km-high) peak at the center of the crater.

Related: NASA's Mars rover discovers "the first strong evidence" of possible fossilized life on the Red Planet.

Known as "Cumberland," the sample examined in the recent study was extracted by Curiosity in 2013 from Yellowknife Bay. Previous examinations revealed that it contains an abundance of clay minerals, sulfur, and nitrates.

However, even after numerous comprehensive examinations, the hydrocarbon chains within the specimen eluded detection for over ten years. These hydrocarbons were inadvertently found during efforts aimed at identifying the protein components—amino acids—in the same sample.

The scientists conducting the recent research decided to experiment with a novel technique for detecting these molecules by first heating up the sample. to 1,100°C (2,012°F) to release oxygen prior to analysis. Their findings revealed an absence of amino acids; however, through sheer chance, they stumbled upon the presence of fatty molecules instead.

I felt an immense thrill when I observed the spikes on the spectrum for the first time," Freissinet stated. "This was simultaneously unexpected yet anticipated. It was unexpected due to the outcomes from the Cumberland sample which we had previously examined numerous times. However, it wasn’t shocking as we had devised a fresh approach to analyzing this particular specimen.

She mentioned, 'A fresh approach led to new outcomes.'

The scientists propose that these molecules could have detached from the lengthy tails of fatty acids known as undecanoic acid, dodecanoic acid, and tridecanoic acid, respectively. Fatty acids consist of extended sequences of carbon and hydrogen atoms ending with a carboxyl (-COOH) acid group.

Life-forming chemistry

To test this theory, the researchers mixed undecanoic acid into a Mars-like clay in the lab before performing a test similar to that carried out by the SAM instrument As expected, the undecanoic acid broke down to decane, indicating that the carbon chains could indeed have originated from fatty acids.

On Earth, molecules like these are overwhelmingly produced by biological processes, but they can also occur naturally without life. However, non-biological processes usually only result in fatty acids with fewer than 12 carbon atoms, the researchers say. While the longest carbon chain detected by SAM had 12 carbons, the instrument is not optimized to detect longer molecules, meaning that it is possible longer chains were also present.

"The findings suggest that liquid water persisted in Gale Crater for extended periods, possibly millions of years or more, providing ample opportunity for prebiotic chemical reactions to occur within these Martian lake settings," stated one of the study’s authors. Daniel Glavin , a researcher at NASA's Goddard Space Flight Center, said in a NASA statement .

Regardless of what made them, the detection of the carbon chains and their likely origins as fatty acids confirms that Curiosity can detect molecules of this kind, and that the molecules can remain preserved for billions of years in the Martian environment. The researchers hope to one day bring samples of Martian soil back home to Earth to properly analyze the contents, and hopefully solve the mystery of the Red Planet's elusive life once and for all.

"We are ready to take the next big step and bring Mars samples home to our labs to settle the debate about life on Mars," said Glavin.

This article was originally published on March 25, 2025

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