Inorganic Interpretation of Luminescent Materials Encountered by the Perseverance Rover on Mars

A major objective of the Mars 2020 mission is to sample rocks in Jezero crater that may preserve organic matter for later return to Earth. Using an ultraviolet Raman and luminescence spectrometer, the Perseverance rover detected luminescence signals with maximal intensities at 330-350 nm and 270-290 nm that were initially reported as consistent with organics. Here, we test the alternative hypothesis that the 330-350 nm and 270-290 nm luminescence signals trace Ce3+ in phosphate and silicate defects, respectively. By comparing the distributions of luminescence signals with the rover detections of X-ray fluorescence from P2O5 and Si-bearing materials, we show that, while an organic origin is not excluded, the observed luminescence can be explained by purely inorganic materials. These findings highlight the importance of eventual laboratory analyses to detect and characterize organic compounds in the returned samples.