Unusual compounds in rocks on Mars may be sign of ancient microbial life

"Unusual features found in rocks on Mars may be the handiwork of ancient microbial life that eked out an existence on the red planet billions of years ago. The rocks were spotted by Nasa's Perseverance rover as it trundled along Neretva Vallis, an ancient river valley that was carved into the landscape by water flowing into the Jezero crater in the planet's distant past. The rover, which touched down in Jezero crater in 2021, encountered the rocks last year as it explored an outcrop called the Bright Angel formation on the northern edge of the ancient valley."

"Our analysis leads us to conclude that the Bright Angel formation contains textures, chemical and mineral characteristics, and organic signatures that warrant consideration as potential biosignatures', they write. Dr Joel Hurowitz, a geochemist and planetary scientist at Stony Brook University in New York, and first author on the paper, said the unusual features on the rocks were accumulations of minerals, including an iron-phosphate mineral, vivianite, and an iron sulphide mineral, greigite. These minerals appear to have formed as a result of reactions between the mud of the Bright Angel formation and organic matter that is also present in that mud, he said."

Perseverance encountered unusual rocks in the Bright Angel formation along Neretva Vallis in Jezero crater that exhibit surface spots and nodules often linked to microbial life on Earth. Onboard instruments detected carbon-based compounds within the rocks. Mineral accumulations include the iron-phosphate vivianite and the iron-sulphide greigite, which appear to have formed from reactions between the mud and organic matter present in that mud. The features could arise from abiotic chemical processes over millennia, but the combination of textures, chemical and mineral characteristics, and organic signatures warrants their consideration as potential biosignatures. Ancient river and lake beds on Mars indicate a once wetter environment where life could have arisen and left traces in rock.

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