ICARUS 38, 166-179 (1979) Thermodynamics of Selected Trace Elements in the Jovian Atmosphere BRUCE FEGLEY, JR. AND JOHN S. LEWIS Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Received October 10, 1978; revised November 30, 1978 The thermochemistry of several hundred compounds of twelve selected trace elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, Tl, In, and Bi) has been investigated for solar composition material along a Jupiter adiabat. The results indicate that AsFa, InBr, TII, and SbS, in addi- tion to CO, PHa, GeH4, AsHs, H~Se, HC1, HF, and H3BO3 proposed by Barshay and Lewis (1978), may be potential chemical tracers of atmospheric dynamics. The reported observa- tion of GeH4 is interpreted on the basis of new calculations as implying rapid vertical transport from levels where T >_ 800°K. Upper limits are also set on the abundances of many gaseous compounds of the-elements investigated. INTRODUCTION The spectroscopic observations of PH3, CO, and possibly GeH4 in Jupiter's atmo- sphere (Ridgway, 1974; Ridgway et al., 1976; Beer, 1975; Larson et al., 1977; Larson et at., 1978; Beer and Taylor, 1978; and Fink et al., 1978) have opened up a new area of research dealing with the use of chemical species as tracers of atmospheric motions. The presence of PH3 and possibly GeH4 is attributed to rapid vertical trans- port of these high-temperature, high-pres- sure species to cool levels in the atmosphere, a process which is faster than the reactions which destroy these gases in the hot lower atmosphere. Prinn and Barshay (1977) have presented a quantitative treatment of the rapid transport model for CO which indicates that the vertical mixing rates pre- viously estimated from heat flux considera- tions are rapid enough to quench the re- duction of CO and make it observable. However, the observed differences in the CO rotational temperature (Beer and Taylor, 1978; Larson et al., 1978) indicate that a stratospheric CO source such as meteoritic infall (Prather et al., 1978) may also be required. It will be difficult if not im- possible to assess the relative magnitudes of different proposed CO sources until data on the vertical distribution profile of CO in the Jovian atmosphere is obtained from a Jupi- ter entry probe such as Galileo. The considerations outlined above and the somewhat distressing fact that kinetic data appear to be lacking for the relevant PH3 oxidation reaction which has been postulated to destroy PH3 in the Jovian atmosphere (Lewis, 1969 ; Prinn and Lewis, 1975) have led us to initiate this study. We have investigated in detail the thermo- chemistry of 12 selected moderately volatile elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, T1, In, and Bi) along a nominal Jovian adiabat in order to suggest possible chemi- cal tracers in addition to those already proposed by Barshay and Lewis (1978). Seven of these elements have not been previously studied, and five were investi- gated by Barshay and Lewis (1978) but 0019-1035/79/050166-14502.00/0 Copyright O 1979 by Academic Press, Inc. All rights of reproduction in any form reserved. 166