Giant columns of organic molecules on Mars may be one of the best signs of life ever

Organic molecules found in Martian rocks cannot be fully explained by non-biological processes, and it is “reasonable to hypothesize” that life could have formed these strange organic molecules, a NASA-led team reports in a new study. However, he cautioned that this does not mean that scientists have found definitive evidence of life on Mars.

In March 2025, scientists reported the discovery of the largest organic molecule ever discovered on Mars. These long chains of hydrogen and carbon may be fragments of fatty acids, which are often produced through biological processes.

In a paper published February 4 in the journal Astrobiology, researchers analyzed how these organic molecules were formed. Using mathematical modeling, information from the Curiosity rover, and data from recent radiolysis experiments that assess how molecules are destroyed by radiation, the researchers turned back the clock billions of years to estimate how abundant the molecules were when they were first deposited.

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A discovery made over 10 years

The organic molecules in question are called alkanes. These are hydrocarbons, long chains of 10 to 12 carbon atoms with multiple hydrogen atoms attached to each carbon. If the end of those names sounds vaguely familiar, it’s because the alkane chemical family includes ethane, methane, propane, and butane. However, these are much shorter strands. Alkane chains with 12 or more carbon atoms are more likely to be created by biological processes.

These fascinating large molecules are embedded in Cumberland Mudstone, a fine-grained sedimentary rock on the bed of an ancient Martian lake called Yellowknife Bay. Curiosity first drilled into the stone in 2013 and has since performed various analyzes using the Mars Sample Analyzer, the ship’s chemistry laboratory.

But it was only about a year ago that researchers discovered the organic molecule after preheating samples to 2,012 degrees Fahrenheit (1,100 degrees Celsius) to look for amino acids. But instead of protein building blocks, researchers found traces of the largest organic molecules ever discovered on Mars.

Rewind the clock with Martian mudstone

In a recent study, researchers turned back the clock on this sample and estimated how abundant these molecules were billions of years ago when they were deposited in the mudstone.

Although the abundance of alkanes in the samples has been measured to be between 30 and 50 ppb, the Cumberland Mudstone has been exposed to the harsh effects of radiation on the surface of Mars for approximately 80 million years. As a result, its organic matter has been degraded by years of bombardment with energetic particles from the sun and throughout space.

“Given the geological history and thermal maturation of the organic matter preserved in the Cumberland samples, it is reasonable to estimate that the recovered material represents only a fraction (perhaps several orders of magnitude less) of the primary lipid content that would have been entrained in the sedimentary unit when it was deposited 2.5 billion years ago,” the researchers explain in their paper.

Using previous radiolysis experiments as an indicator, the researchers calculated a “conservative” initial abundance of alkanes, or fatty acids from which alkanes are fragmented, between 120 and 7,700 ppb. So, are significant amounts of these substances explained by abiotic sources, or were they formed through biological processes?

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The researchers evaluated numerous scenarios. First, they investigated space-based origins. Interplanetary dust particles (IDPs) and meteorites frequently transport organic molecules to the surface of Mars. However, the researchers concluded that these processes were unlikely to explain the richness of organic matter in the Cumberland samples, as IDP cannot penetrate the rock and there is no sign of a meteorite impact.

In the second scenario, organic molecules settle to the surface after separating from the atmosphere, but Mars’ ancient atmospheric fog was not foggy enough to account for the observed abundances.

Smaller organic molecules are usually produced, although water-rock interactions may have contributed. Fatty acid molecules can occur via different routes. But that requires high temperatures, and Cumberland has no evidence of proper heating.

Evidence of alien life?

Despite these excluded theories, one non-biological process retained water. The researchers cannot rule out the possibility that some of the organic material formed abiotically in Mars’ hydrothermal systems and was transported to the surface by organic-rich fluids such as water.

“To be clear, we do not claim that evidence of ancient Martian life has been found in the Cumberland mudstones,” the researchers wrote in their paper.

Still, Cumberland’s sample is enriched with many molecules that are thought to be biologically relevant. These include clay minerals that form in the presence of water, nutritious nitrates, a type of carbon associated with biological processes, and sulfur, which helps preserve organic molecules.

Gale Crater, the site of Yellowknife Bay, also held water for countless millions of years, ostensibly giving life-forming chemistry plenty of time to mix and match numerous molecules.

But the Curiosity rover may be limited in its ability to analyze larger molecules, which are more likely to be associated with biological processes, because molecules need to be separated and identified. “There are always tradeoffs” in such analyzes even on Earth, study co-author Christopher House, professor of geosciences in Penn State’s College of Earth and Mineral Sciences, told Live Science in an email. “So while Curiosity may be able to find larger organic molecules, [precision] Therefore, the identification of these specific molecules became convincing. ”

The next step is to carry out experimental studies on Earth that mimic the Cumberland Mudstone and the Martian environment to see how organic molecules such as fatty acids react to Martian conditions. (The ultimate goal is for scientists to obtain real Martian mudstone through a Mars sample return mission, but for now it’s a vague proposition at best.)

The existence of past or present Martian life is also vague, but there is reason for optimism among ET enthusiasts. “The researchers say it is reasonable to hypothesize that living organisms may have formed the organic compounds because the non-living sources they considered do not fully explain the abundance of organic compounds,” NASA officials said in a statement.

Coincidentally, the microbial processes that may have produced these organic materials may have appeared on Earth at about the same time in the Archean era. Given that the Perseverance rover also discovered a potential biosignature in 2025, the answer to the ultimate question is more appealing than ever.