NASA's Perseverance rover has detected evidence of organic compounds in a huge 28-mile-wide crater on Mars for the first time.
The discovery, which was published in the journal Nature, has implications in the search for potential biosignatures—or signs of life—on the Red Planet, researchers said.
Organic molecules are chemical compounds that are made primarily of carbon and hydrogen and often other elements like oxygen, nitrogen, phosphorus and sulfur.
"They are an exciting clue for astrobiologists since they are often thought of as building blocks of life," Joseph Razzell Hollis, a postdoctoral fellow at London's Natural History Museum and an author of the paper, told Newsweek.
"Importantly, they can be created by processes not related to life as we know it, and so organic molecules are not evidence of life on their own without sufficient extra evidence that cannot be explained by nonbiological—or abiotic—processes," he said.
Perseverance detected evidence of diverse types of organic compounds in the huge Jezero crater, which the rover has been exploring since it landed on Mars in February 2021. Perseverance is the first Mars mission to explore the crater.
Scientists believe this crater, which was created from a meteorite's impact, was once the site of an ancient lake, probably around 3 billion to 4 billion years ago. It is thought that the conditions in this lake basin may have been favorable to life.
As the authors of the paper describe, the rover detected signatures in the crater floor rocks that are consistent with a range of different organic molecules containing one or two rings of carbon. (The scientists could not say for sure exactly what kinds of organics were detected.)
"While these kinds of molecules can occur naturally through purely nonbiological processes and are therefore not evidence of past life, they are still exciting to discover because they highlight the variety of organics that may have survived on Mars even after billions of years of degradation," Razzell Hollis said.
He continued: "Seeing that the possible organic signals differ in terms of type, number of detections and distribution between the different geological units of the crater floor was surprising and exciting for us because it opens the possibility of different formation, preservation or transportation mechanisms across the crater and, more broadly, the surface of Mars."
As scientists get more data from Mars, they are gaining a clearer picture of the variations across its regions, providing a more comprehensive understanding of organic compounds on the Red Planet. This will help them understand whether life could have ever evolved there, according to Razzell Hollis.
The organic signatures were detected with an instrument on Perseverance known as SHERLOC, which stands for Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals. This instrument is the first tool to enable fine-scale mapping and analysis of organic molecules on Mars.
Organic molecules can be formed in multiple ways, including nonbiological processes like delivery by interplanetary dust or meteorite impacts, volcanic processes or water-rock interactions. In the case of the current study, it's not clear what the origin of the organic molecules is.
"With the data we currently have, we can't be certain which process dominated in any given situation, but we see multiple signals consistent with organics that appear to vary across the units of the crater floor and in the minerals they are spatially associated with," Razzell Hollis said. "Things do not look the same everywhere in Jezero, and that is exciting."
He went on: "As planetary scientists and astrobiologists, we are very careful with laying out claims—claiming that life is the source of organics or possible biosignatures is a 'last resort hypothesis,' meaning we would need to rule out any nonbiological source of origin."
Nevertheless, the results add to past observations from other missions, providing more information about the history of the Jezero crater and indicating that more complex geochemical processes were taking place than previously thought.
"We are intrigued by these signals since they could be organic and would point to the possibility that building blocks of life could have been present for a long time on the surface of Mars, in more than one place," Razzell Hollis said. "We would need [to wait for the samples' return] to confirm the presence, type and mineral associations of organic molecules before we can consider whether they are specific evidence of past life."
Intriguingly, the rover has cached eight sample cores from the various rocks that the authors examined in the paper, which will hopefully be brought back to Earth by the Mars Sample Return mission. The mission could launch as soon as 2027.
"So far, the only Martian rocks we've ever been able to study on Earth have been meteorites. Getting our hands on intact Mars rocks, carefully stored and protected from contamination, will be invaluable to planetary science," Razzell Hollis said.
He went on: "We will be able to study them in far greater detail than the rover is capable of and hopefully answer some of the bigger questions about whether or not Jezero once contained the building blocks of life. But most importantly, we will know exactly where each of these samples came from on Mars.
"That geological context will help us better understand the results we gather from them like nothing before," he said.
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Aristos is a Newsweek science reporter with the London, U.K., bureau. He reports on science and health topics, including; animal, ... Read more
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