Journal of Radioanalytical and Nuclear Chemistry, Vol. 238, Nos 1 2 (1998) 11~121 Strange xenon in Jupiter O. Manuel,* K. Windier, A. Nolte, L. Johannes, J. Zirbel, D. Ragland Departments of Chemistry, Chemical Engineering, Metallurgical Engineering, Physics, Geology and Geological Engineering, University of Missouri, Rolla, Missouri 65401, USA (Received June 17, 1998) Jupiter's helium-rich atmosphere contains xenon with excess 136Xe and the ratio of r-products more closely resembles "strange" xenon (Xe-X, alias Xe-HL) seen in carbonaceous chondrites than xenon seen in the solar wind (SW-Xe). The linkage of primordial helium with Xe-X, as seen on a microscopic scale in meteorites, apparently extended across planetary distances in the solar nebula, This is expected if the solar system acquired its present chemical and isotopic diversity directly from debris of the star that produced our elements. Introduction* In January of this year, GOLDIN 1 ordered the release of mass spectrometer data from the 1995 entry of the Galileo probe into Jupiter. One can find the data on the internet at the web address: http://webserver.gsfc.nasa.gov/code915/gpms/datasets/gpm sdata.html. The Galileo Probe Mass Spectrometer took readings every 0.50 seconds, 2 producing signals for mass/charge (re~q)=2-150. This includes all stable noble gas isotopes. Signals for noble gas isotopes at mass/charge (re~q)=21, 40, 78, 124 and 126 are difficult to distinguish from background and those at m/q = 20, 22, 36, 38, 80, 82, 84 and 86 displayed significant variations. Contamination may have resulted from incomplete adsorption of hydrocarbons by Carbosieve, the material used in the enrichment cells. 2 Thus, the most reliable results lie in the high mass region that includes xenon, the noble gas of choice. What makes xenon the noble gas of choice ? Besides the fact that it has more stable isotopes than any other noble gas and lies in the region of the mass spectrum that has the least contamination, it has also provided the most information about the early history of the solar system and the origin of its elements. Xenon isotopes contain decay products of the first two extinct radionuclides 3,4 discovered in the solar system in the 1960s. In 1960, xenon provided the first hint that isotopic ratios of primordial elements might vary within the solar system, 5 and xenon isotopes first carried the message in 1972 that one form of xenon, Xe-X, might have been "...added to our solar system from a nearby supernova, although no evidence for the addition of products from a separate nucleosynthesis event has been found in other elements." (see Reference 6, p. 100) Soon after confirmation 7 of excess 124,126Xe and 134,136Xe in the Allende meteorite from the p- and r-processes of nucleosynthesis, 8 xenon isotopes in the Murchison meteorite revealed a complementary component, 9 Xe-S, characterized by excess 128-132Xe from the s-process of nucleosynthesis. 8 More important for the present study are the finding 1~ and confirmation 11 that primordial He is always closely coupled with isotopically strange Xe-X in meteorites. Mineral separates of the Allende carbonaceous chondrite illustrate this close coupling 1~ of primordial He with xenon of strange isotopic composition (Fig. 1). The isotopic ratio on the vertical axis, 136Xe/134Xe, consists of isotopes that are only produced in the r- process. 8 The elemental ratio on the horizontal axis consists of the nuclide widely rated as second most abundant in the solar system, 4He, and the reference xenon isotope, 134Xe. Linkage of primordial 4He with Xe-X is seen in all classes of meteorites, 11 and in each case isotopic ratios extrapolate to xenon of "normal" isotopic composition as elemental abundances of He vanish. J 1,1- 1 .o5 0.95 0.9 0.85 0.8. 0,75. % x 20000 40000 60000 80000 100000 120000 140000 160000 4He/134Xe Fig. 1. Values of the 136Xe/134Xe ratio in diverse meteorites 11 correlate with abundances of primordial He. The data shown here are mineral fractions of the Allende meteorite from LEWIS et al. 7 The most extreme data point in the upper right comer is mineral fraction, 3CS4. Other isotopic ratios of xenon in 3CS4 are shown in Table 1 * E-mail: om@umr.edu 0236 5731/98/USD 17.00 9 1998 Akaddmiai Kiad6, Budapest All rights reserved Elsevier Science B. K, Amsterdam Akad~miai Kiad5, Budapest