The Ne-Xe abundances in Jupiter

The Galileo probe mass spectrometer also showed that the abundances of the four heavier noble gases in Jupiter s atmosphere relative to H are distinctly non-solar (Table 7). Ne is depleted by about an order of magnitude, whereas Ar, Kr, and Xe all are enriched by a factor of 2.5. The striking underabundance of Ne is viewed as supporting evidence for He segregation in Jupiter s interior (Niemann et al. 1998 von Zahn et al. 

Jupiter is the only giant planet for which isotopic ratios of noble gases are available, provided by the Galileo probe mass spectrometer (Mahaffy et al. 1998 2000 Table 7). This instrument also yielded quite precise values for D/H, and which are 

The D/H ratio of (2.6 0.7) x 10 (Niemann et al. 1998, Table 7) agrees within error limits with the inferred but more precise value of (1.94 0.39) x 10 determined from He measurements in the solar wind and Jupiter Sun section. Table 3). Implications of this result for galactic evolution and cosmology are discussed by Gloeckler and Geiss (2000) and Niemann et al. (1998) (see also the Sun section). 

The isotopic compositions of Ne, Ar, and Xe as measured by the Galileo probe mass spectrometer (Table 7) are within error limits identical to solar wind values (Tables 4 and 5). The most precisely measured ratio, Ar/ Ar, almost perfectly agrees with values determined for solar wind with lunar and meteoritic samples and the SOHO spacecraft. The interpretation of this similarity is not as straightforward as it may seem, however. First, within its uncertainty, the Jupiter value is also very close to the terrestrial atmospheric ratio or that of primordial meteoritic Ar usemann et al. 2000 see Ott 2002, this volume). Second, we noted in the Sun section that Ar/ Ar in the solar wind may be up to a few percent higher than the bulk solar value. Third, Ar trapped in water ice at -30 K in the laboratory shows a depletion of the lighter isotope of 1.4-1.9%/amu (Notesco et al. 1999). Therefore, if Jupiter s Ar has been delivered predominantly by cold icy planetesimals, as is indicated by its 

1 Hofmann et al. 1980a. 2 Hofmann et al. 1980b. 3 Donahue and Russell 1997. 4 Donahue and Pollack 1983. 5 Istomin etal. 1983. 

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