In the search for life beyond Earth, NASA’s Perseverance Mars rover has discovered a rock sample that could preserve evidence of ancient microbial life
The sample, known as “Sapphire Canyon,” was collected from a rock formation called “Cheyava Falls” in July 2024. This discovery, published in the journal Nature is one of the most promising leads in astrobiology to date.
Ancient riverbed provides clues.
The rock was found in the Bright Angel formation within Neretva Vallis, a dried-up river valley that once carried water into Mars’ Jezero Crater. The site was chosen for exploration because of its history with water.
Sapphire Canyon was formed from sedimentary rocks made of clay and silt, materials that, on Earth, are well known for preserving microscopic life. These rocks also contain organic carbon, sulfur, oxidised iron (rust), and phosphorus, chemical elements that are crucial for life as we know it.
Signs of a chemical energy source
Using its advanced tools, PIXL and SHERLOC, Perseverance detected colourful mineral spots on the surface of the rock. These spots were found to be arranged in distinct patterns known as reaction fronts, areas where physical and chemical interactions occur. Scientists observed iron-rich minerals such as vivianite and greigite, both of which are associated with biological activity on Earth.
Vivianite often appears in wetlands and decaying organic material, while greigite can form as a result of microbial activity. Together, these minerals could indicate past microbial life, as they may have formed through reactions involving organic matter and the Martian environment.
Biological or geological origins?
Although the presence of these minerals is evident, it is not definitive proof of life. Both vivianite and greigite can also be formed through non-biological processes. However, this process usually requires high temperatures or acidic environments, which do not appear to be present in the Bright Angel formation.
The absence of these harsh conditions raises the likelihood that the minerals may have formed through biological means. The findings suggest that electron-transfer reactions, commonly used by microbes to generate energy, could have occurred in this Martian rock.
Scientists have always believed that any evidence of life would be locked in much older rocks until now. This new finding opens up the possibility that Mars remained habitable later in its history than previously thought.
Sapphire Canyon is one of 27 rock cores collected by Perseverance since its landing in February 2021. Each sample is a vital piece of the puzzle in understanding the planet’s history, and possibly its biology.
The search for life
The sample will eventually be returned to Earth as part of NASA’s future Mars Sample Return mission. Scientists will then conduct more detailed studies to determine whether the biosignatures are truly biological in origin or the result of natural geological processes.