NASA reports that the ALICE spectrograph on the Rosetta space probe studying comet 67P/Churyumov–Gerasimenko (67P) determined that electrons (within 1.0 kilometers above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.