The Perseverance rover has detected macromolecular carbon, large, cross-linked networks of reduced organic material, at multiple locations across the floor of Jezero Crater, according to a study published June 24 in Science Advances. The detection, made by the SHERLOC instrument (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) on the rover’s robotic arm, represents the most robust organic detection in Jezero crater so far: hundreds of individual detection points across four targets on three distinct rocks.
Lead author Ashley E. Murphy of the Planetary Science Institute and colleagues identified the carbon through its Raman G-band spectral signature, a peak centered at 1,591-1,606 wavenumbers with a width of 79-136 inverse centimeters. The peak parameters rule out graphite and closely resemble the carbon found in carbonaceous meteorites, coal, and terrestrial microbialites. The material was detected at shallow depths: on abraded surfaces at the Apollo Temple and Walhalla Glades targets, and, for the first time, on a dust-cleared natural rock surface at Cheyanna Falls, meaning the organic material sits just microns below the surface.
What it is and what it is not
The detected material is macromolecular carbon (MMC), a class of refractory, reduced carbon compounds that form large, disordered networks. It is not a specific molecule like an amino acid or lipid, and critically, SHERLOC’s Raman spectroscopy cannot determine whether the carbon is biological or abiotic in origin. The paper explicitly states that in-situ Raman analyses “cannot determine whether these organics denote abiotic or biotic sources.”
The competing explanations are numerous. The carbon could have been delivered by meteoritic infall, carbonaceous chondrites and interplanetary dust particles are known to carry similar organic material. It could have formed through abiotic organic synthesis via serpentinization, a water-rock reaction that produces hydrogen which then reduces carbon dioxide to organic compounds. Hydrothermal activity, electrochemical reduction of carbon dioxide, and impact-generated carbon are all on the table. As the authors write, “There are multiple potential pathways to form abiotic organics on Mars.”
Widespread and layered
The detection spans a distance of more than 3,200 kilometers from Gale Crater, where the Curiosity rover has previously detected organic compounds. The mineral associations at Jezero are particularly informative: MMC was found with both primary silicates (suggesting it was deposited during the original sedimentation) and with secondary carbonate and sulfate minerals (indicating a later diagenetic event). This implies at least two separate episodes of organic matter emplacement or formation, separated in time.
One of the key samples, the Cheyava Falls core, cached for the future Mars Sample Return mission (“Sapphire Canyon”), contains organics at a location that has also generated intense interest for its “leopard spot” textures, previously described as potential biosignatures by Hurowitz et al. in Nature (2025). If this core is returned to Earth, isotopic analysis of its carbon (specifically the 13C/12C ratio) could distinguish between biological and abiotic origins in a way that SHERLOC cannot.
What comes next
The SHERLOC team, co-led by deputy principal investigator Kyle Uckert of NASA’s Jet Propulsion Laboratory, continues to survey Jezero’s western fan and margin units. The detection of MMC on a natural, unbrushed rock surface suggests that the carbon is more accessible than previously assumed, a finding that could influence sample selection strategies for the remainder of the mission.
Isotopic characterization, which could settle the biological versus abiotic question, requires sample return. In the meantime, the paper provides the strongest evidence yet that complex organic carbon is widespread across ancient Martian environments, a necessary, if not sufficient, condition for the hypothesis that Mars once hosted life.
Source: Murphy, A.E., Uckert, K., Hand, K.P. et al. Spatially distributed complex organic matter detected in an ancient river valley in Jezero crater, Mars. Science Advances (2026). DOI: 10.1126/sciadv.adx0047