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Published November 2010 | public
Journal Article

Abundances of Jupiter's trace hydrocarbons from Voyager and Cassini


The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C_2H_2) and ethane (C_2H_6). The spatial variation of these gases is controlled by both chemistry and dynamics, and therefore their observed distribution gives us an insight into both processes. We find that the two gases paint quite different pictures of seasonal change. Whilst the 2-D cross-section of C_2H_6 abundance is slightly increased and more symmetric in 2000 (northern summer solstice) compared to 1979 (northern fall equinox), the major trend of equator to pole increase remains. For C_2H_2 on the other hand, the Voyager epoch exhibits almost no latitudinal variation, whilst the Cassini era shows a marked decrease polewards in both hemispheres. At the present time, these experimental findings are in advance of interpretation, as there are no published models of 2-D Jovian seasonal chemical variation available for comparison.

Additional Information

© 2010 Elsevier Ltd. Received 27 November 2009; revised 10 May 2010; accepted 14 May 2010. Available online 24 May 2010. The acquisition of CIRS data is the result of the collective efforts of a large number of people, including the following who worked on various aspects of CIRS science planning, instrument commanding, uplink, calibration and databasing: S.B. Calcutt, R.C. Carlson, M.H. Elliott, E. Guandique, M. Kaelberer, V.G. Kunde, E. Lellouch, A. Mamoutkine, P.J. Schinder, M.E. Segura, J.S. Tingley, and also many engineers and science planners at the Jet Propulsion Laboratory. We would like to thank R.A. West, A.J. Friedson and Y.L. Yung for helpful discussions during the preparation of this manuscript. During the research for and writing of this report, R.K.A. and F.M.F. were funded by the NASA Cassini Project, and C.A.N. and M.A. were supported by the NASA Outer Planets Research Program. Portions of this work were carried out by the Jet Propulsion Laboratory, under contract with the National Aeronautics and Space Administration.

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