Mars Rover Spots Complex Carbon on the Red Planet, Marking Yet Another Detection of a Building Block of Life
Along with other recent discoveries, the new finding from Perseverance boosts the case that Mars once hosted conditions that could support living things—but it isn’t a definitive sign of ancient organisms
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NASA’s Perseverance rover has detected complex molecules of carbon on the surface of Mars.
These compounds, known as macromolecular carbon, can be produced by living organisms, though that’s not the only way they might form. Researchers identified them in the Bright Angel outcrop, a rocky area of Mars that contains the “most robust” detections to date of organic material in the red planet’s Jezero Crater, according to a new paper published June 24 in the journal Science Advances.
While these carbons are associated with fossilized microbes on Earth, the discovery isn’t a definitive sign of life. Organic carbon can come from geochemical processes without any living things involved. It might have been transported to the planet by meteorites or been generated in reactions between rocks and water.
For the time being, the finding offers “more tantalizing information” about the conditions in the Bright Angel rocks, John Bridges, a planetary scientist at the University of Leicester in England who was not involved in the study, tells the Guardian’s Ian Sample.
“Finding these organic macromolecules on Mars and other planetary bodies helps us determine whether the necessary chemical ingredients and environmental conditions to support life have ever existed there,” study co-author Ashley Murphy, a researcher at the Planetary Science Institute, tells New Scientist’s Alex Wilkins.
Perseverance has been searching Jezero Crater for signs of past life since 2021. Researchers think that the 28-mile-wide impact crater once hosted an ancient lake, where a long-gone river deposited rocks and sediment. It’s a top candidate for an environment that could have once been habitable on Mars, and Perseverance has already found promising evidence.
Last year, NASA officials said the rover had uncovered the “clearest sign” yet of ancient life on Mars: a rock, called Cheyava Falls, with organic material and dark markings that are linked to microbial activity on Earth. For the new study, the rover examined the Cheyava Falls mudstone and other nearby sites.
With a technique called Raman spectroscopy, the Perseverance rover’s SHERLOC instrument illuminated the rock samples with a laser and mapped the organic compounds and minerals within. Across two Martian mudstones, the data revealed hundreds of organics, including the complex carbons.
The carbons were found only microns below the planet’s surface—a depth thinner than a sheet of paper, per a statement from the Planetary Science Institute about the discovery—so it came as a surprise that they were relatively well-preserved. This suggests either that the rocks were recently exposed or that the organic materials are resistant to radiation and other processes that might have otherwise degraded them over time.
In one mudstone, the team found that the complex carbons were associated with carbonate and sulfate minerals, which can form in water-rich conditions. “It’s giving us information about the geological context of where those organics are being found,” Lewis Dartnell, an astrobiologist at the University of Westminster in England who was not involved in the study, tells New Scientist. Another mudstone showed an association between the carbons and sediment that is rich in silicates.
Did you know? The first discovery of Mars organics
NASA’s Curiosity rover made the first definitive detection of organic matter on Mars in 2014, and since then, rovers have continued to unveil similar hints to the red planet’s past.
Prior to this discovery, macromolecular carbon had only been seen in Mars’ Gale Crater, which is being explored by NASA’s Curiosity rover. In April, scientists announced that Curiosity had found the most diverse suite of organic molecules ever identified on the red planet, including materials that are building blocks of life on Earth. Perseverance’s new detections of macromolecular carbon were made roughly 2,000 miles away from Curiosity’s discovery in Gale Crater, suggesting that organic material may have once been widespread in ancient Martian rivers and lakes.
“We now have two definitive locations on Mars identified where there’s identifiable organic matter in mudstones,” says Christopher House, a geoscientist at Penn State University who worked on the Curiosity findings but was not involved in the newest study, to Chemical & Engineering News’ Ana Georgescu. “People thought that the soils on Mars didn’t have much organic matter, but they do.”
While Perseverance can tell that organic carbon is present in the rock, it can’t go much deeper into what makes up the compounds. The technology required to probe the sample for life—and unveil any fossils of microbes that might be there—is not available on any Mars rover. Instead, a future mission will have to collect the material and tote it back to Earth, where energy-intensive and sizeable equipment can analyze it in full.
“These treasure troves of information are puzzles that need to be solved,” study co-author Mark Sephton, an astrobiologist and organic geochemist at Imperial College London, tells the Guardian. “And that is best done back in Earth laboratories after sample return.”