Perseverance found complex macromolecular carbon sitting directly on the surface of a Martian rock at Bright Angel, an outcrop on the edge of the ancient river channel Neretva Vallis. After five years drilling and abrading rocks in Jezero Crater to find organic carbon buried inside them, this is the shallowest detection of organic matter on the Martian surface to date, according to lead author Ashley E. Murphy of the Planetary Science Institute in Tucson.
The detection came from SHERLOC, a deep-ultraviolet Raman spectrometer on Perseverance's robotic arm that fires a UV laser and reads the shifted energy of reflected light to identify specific molecular bonds. On Earth, this concentration of macromolecular carbon typically points to a biological origin. On Mars, the source is unknown.
The full study is worth reading not for the conclusion, which is deliberately inconclusive, but for what the ambiguity reveals about the limits of in-situ analysis. Murphy's team cannot determine whether this carbon is biological, geological, or the product of ancient chemistry without physically returning the samples to Earth. That is the real story here: a five-year mission producing its most significant surface find, and the answer still requires a sample return mission that does not yet exist.
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