Conclusion

From the projects covered in this chapter it can be seen that the study of giant planet atmospheres will continue to be provided for many years with a large amount of ever increasingly accurate measurements with which theories may be tested. The improvements in our understanding of these worlds that are expected, or hoped for, will now be briefly summarized.

Jupiter

The Galileo and Cassini spacecraft provided an enormous quantity of data on the largest of the giant planets, and these data are still being analyzed. Indeed, as knowledge of the spectroscopy of Jovian gases and candidate aerosols improves, both through better modeling and new laboratory studies, these data, and the data from the previous Voyager missions, are likely to be reanalyzed for many more years to come. Particular advances in spectroscopy that are expected are improvements in the knowledge of cold-temperature ammonia and methane gas absorption in the near-infrared, and new measurements of the real and imaginary refractive indices of Jovian candidate aerosols such as NH3, NH4SH and (NH4)2S. Clearly, retrievals of planetary spectra are of limited value when the absorption spectra of candidate absorbers are themselves somewhat unclear, and such studies will greatly improve the accuracy of existing Jovian analyses. Together with the analysis of existing data, new spacecraft observations are planned and in particular the Juno spacecraft, arriving in 2016, will map Jupiter's internal structure, hopefully determining if it has an icy/rocky core, and will also make detailed measurements of Jupiter's North Pole to see if Jupiter, like the other giant planets (except Uranus) has a warm cyclonic vortex there.

In parallel with the continued analysis of spacecraft data, the quality of ground-based data continues to improve. One particular advantage of ground-based observations of significance to Jovian studies is the ability to observe at very high spectral resolution and thus observe individual absorption lines. For example, such

Figure 8.13. Artist's impression of ESA's proposed Darwin nulling interferometer mission (Alcatel study). Courtesy of NASA

studies have led to a significantly more accurate determination of the (D/H)CH4 ratio by observing close, near-equal strength CH4 and CH3D lines (Bezard et al., 2003).

Finally, the ability to model the dynamics of the giant planets continues to improve. Numerical models such as EPIC (Dowling et al., 1998) have been developed which provide new tools for analyzing existing dynamical observations. General circulation models (GCMs), originally developed for terrestrial weather forecasting, are currently being modified for giant planet studies which should help in the interpretation of observations by spacecraft and by ground-based observatories.

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