Evidence of Ancient Life on Mars: Discovery of Complex Carbon Compounds

NASA’s Perseverance rover has made a groundbreaking discovery of complex carbon compounds in a Martian crater, specifically in the Bright Angel Formation. These compounds might be indicative of past life, displaying promising connections to ancient biological activity, although they have also been found in non-biological environments like meteorites.

During its 2024 mission, Perseverance explored a rocky area near an ancient riverbed that once nourished a lake in Jezero Crater. Some photographed rocks exhibited peculiar mottling patterns, dubbed “leopard spots” or “poppy seeds” by NASA scientists. These designs, consisting of dark circular blotches up to 1 millimeter in size, bear resemblance to traces left by ancient microbial life on Earth.

While abiotic origins can’t be eliminated, the discovered patterns present some of the most compelling evidence of potential ancient life on Mars. However, scientists seek more detailed insights regarding the chemical composition and distribution of these patterns within the Bright Angel Formation.

Equipped with advanced instruments, including the SHERLOC tool, Perseverance has the capacity to analyze the chemical composition of Martian rocks. The SHERLOC instrument utilizes reflected light from an ultraviolet laser to identify various elements and compounds within rock samples.

Researcher Ashley Murphy from the Planetary Science Institute in Tucson, Arizona, employed SHERLOC to detect large, complex carbon-containing molecules known as polymeric carbon both on a marked rock in the Bright Angel Formation and another rock located approximately 100 meters away.

“On Earth, polymeric carbon is generally found in ancient rocks and in some instances, it represents the sole organic evidence of bygone microbial life,” says Murphy. “Discovering these organic macromolecules on Mars is pivotal in determining whether the chemical essentials and environmental conditions that could support life ever existed there.”

It’s crucial to highlight that the presence of these carbon compounds does not imply a biological origin, as they have also been discovered in meteorites, notes Lewis Dartner at the University of Westminster, London. Yet, Murphy’s team found a significant association between these compounds and carbonate and sulfate minerals, which typically form in water-rich environments. “This gives vital geological context for where the organic materials are located,” explains Dartnell.

Jezero Crater is believed to have harbored considerable amounts of water at some point in its history, so the finding of these carbon compounds is relatively unsurprising. However, as Kyle Uckert at NASA’s Jet Propulsion Laboratory in California notes, polymeric carbon has never before been observed on such rocky surfaces on Mars, suggesting it may exhibit unique resistance and characteristics compared to other carbon compounds on the planet.

“The widespread presence of this polymeric carbon within the Bright Angel mudstone is unexpected compared to findings elsewhere in the crater,” Uckert observes. The reason for this prevalence remains unclear, but Dartnell states it is a positive sign that further indications of past life might still be uncovered. “This detection confirms that complex organic materials like these polymeric deposits can endure for extended periods.”

While the SHERLOC instrument effectively identifies polymeric carbon, it does not provide detailed insights into the specific composition of the compounds beyond indicating they are carbon-rich. Sean McMahon from the University of Edinburgh, UK, emphasizes, “To determine whether the carbon in these rocks is biologically derived, we will need to return samples to Earth.”