Mysterious Carbon-Rich Rock Found on Mars
▼ Summary
– NASA’s Perseverance rover detected complex macromolecular carbon on the surface of a rock at Bright Angel, the shallowest detection of organic matter on Mars to date.
– The carbon was found at an outcrop on the edge of the ancient Neretva Vallis river channel in Jezero Crater, using SHERLOC’s UV laser spectrometer.
– Three targets (Cheyava Falls, Apollo Temple, and Walhalla Glades) showed a graphitic band signal, indicating a resistant network of reduced carbon atoms.
– The material roughly matches terrestrial kerogen, but researchers avoid that term because it implies a biogenic source, whereas the carbon’s origin is unknown.
– On Earth, similar macromolecular carbon usually suggests a biological origin, but determining the source of the Bright Angel carbon may require sample return to Earth.
NASA’s Perseverance rover has spent five years combing Jezero Crater for chemical evidence of what shaped Mars billions of years ago. The rover has detected organic carbon before, but always inside rocks that needed drilling or abrasion to reveal it. Now, at an outcrop along the edge of an ancient river channel called Neretva Vallis, Perseverance has identified complex macromolecular carbon sitting directly on the rock’s surface.
“To our knowledge, that’s the shallowest detection of organic matter on Martian surface to date,” said Ashley E. Murphy, a researcher at the Planetary Institute in Tucson, Arizona, and lead author of the study on the rock, discovered at a site known as Bright Angel. On Earth, this level of macromolecular carbon typically points to a biological origin. But figuring out what this Bright Angel carbon actually is, and where it came from, may require bringing samples back to Earth.
Carbon on the rocks
The Bright Angel carbon detection came from SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), a UV Raman spectrometer mounted on Perseverance’s robotic arm. SHERLOC fires a deep-ultraviolet laser at a target and reads the light that returns at shifted energies, a signal that lets scientists identify specific molecular bonds.
Between sols 1180 and 1218, the rover aimed this UV laser at four targets at Bright Angel. One, named Steamboat Mountain, was an ordinary rock used as a control. The other three,Cheyava Falls, Apollo Temple, and Walhalla Glades,returned a spectroscopic signature of macromolecular carbon. This signal, known as the graphitic band (G-band), indicates a tangled, cross-linked network of mostly reduced carbon atoms that resists chemical and thermal breakdown.
Within the precision limits of Perseverance’s instruments, the material roughly resembles terrestrial kerogen. But the researchers decided against using the word “kerogen.” On Earth, kerogen is made almost exclusively from biological matter, mainly fossilized microbes buried millions of years ago. “The term kerogen implies biogenic source,” Murphy explained. “Macromolecular carbon implies we don’t know whether its origin is biotic or abiotic.”
(Source: Ars Technica)
