The rate coefficient for the quenching of metastable O(1S) atoms by O2 has been measured as a function of temperature from 250 ¿K to 550 ¿K. The resulting Arrhenius expression, K1=4.9¿10-12 exp[-(885¿35)/T>, is in good agreement with previous laboratory work. It is suggested that the much larger value for k1 inferred from an analysis of the artificial auroral experiment, Precede, is due to overestimating the contribution to O(1S) production from O2+ dissociative recombination. The possibility that O(1S) atoms are produced only by the dissociative recombination of vibrationally excited O2+ ions is discussed; such excited ions would not exist at the altitude of the Precede experiment because of the rapid cooling of these ions by resonant charge transfer processes.