Martian Rock Surface Contains Carbon – Origin Uncertain
NASA's Perseverance rover has detected complex macromolecular carbon on the surface of a Martian rock, a find that on Earth would typically signal biological origins, but its source on Mars remains unknown.
After five years exploring Jezero Crater, NASA's Perseverance rover has made a surprising discovery: organic carbon sitting on the surface of a rock, rather than buried inside. The finding occurred at an outcrop named Bright Angel, on the edge of an ancient river channel called Neretva Vallis. According to lead author Ashley E. Murphy of the Planetary Institute in Tucson, Arizona, this represents the shallowest detection of organic matter on the Martian surface to date.
The detection was made using SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), a UV Raman spectrometer mounted on the rover's robotic arm. SHERLOC fires a deep-ultraviolet laser at a target and analyzes the returned light to identify specific molecular bonds. Among four targets examined at Bright Angel, three—Cheyava Falls, Apollo Temple, and Walhalla Glades—showed a spectroscopic signature of macromolecular carbon known as the graphitic band (G-band). The fourth target, Steamboat Mountain, served as a control and showed no such signal.
The material's structure resembles terrestrial kerogen, which on Earth is almost exclusively derived from biological matter, such as fossilized microbes. However, the researchers deliberately avoid the term "kerogen" because it implies a biogenic origin. "The term kerogen implies biogenic source," Murphy explained. "Macromolecular carbon implies we don’t know whether its origin is biotic or abiotic."
To determine the true nature of the Bright Angel carbon, scientists say sample return missions will be essential. The precision of Perseverance's instruments is insufficient to conclusively establish whether the carbon was produced by life or by non-biological processes.
