DETECTION OF (H2O)-O-18 IN JUPITER

We report the detection of a single line of (H2O)-O-18 in Jupiter at 1 980.76 cm(-1), the first detection of O-18 in Jupiter. Models of the s pectrum of Jupiter near this line imply that the Jovian isotopic abund ance ratio O-18/O-16 is 1-3 times the terrestrial value. It is not pos sible to distinguish between the terrestrial ratio and highly anomalou s oxygen isotope ratios of 2 or 3 times terrestrial because of the dif ficulties in modeling the spectrum and our reliance on a single (H2O)- O-18 feature. Anomalous O-18 in Jupiter could be caused by an intrinsi c oxygen-isotope heterogeneity between solid and gaseous reservoirs in the preplanetary nebula, although given the constancy of O-16/O-18 in other solar system objects, such an explanation seems unlikely. Neith er the isotopic anomalies in individual meteorite grains nor the diffe rences in isotopic ratios between those in the solar system and in the interstellar medium would explain a gross enhancement of O-18 in the outer solar system. The Galileo Probe Mass Spectrometer experiment may not allow a more accurate abundance determination of (H2O)-O-18 becau se of the much larger amount of interfering Ne-20 that may be present. It appears that no lines of (H2O)-O-17 are detectable in the 5 mu m w indow.