Prof. Patrick Irwin

Abstract:

The highly organized and brightly coloured cloud structure on the nearest and largest gas giant planet Jupiter has been explored by the Galileo orbiter/probe project, which completed its nominal mission in December 1997. At least four and possibly as many as six distinct layers of haze or cloud, of different composition and at different depths, appear to contribute to the external appearance of the planet at low and mid-latitudes. A model of the properties of these clouds has been developed from the various data and theoretical constrains. Aspects of the global and time variability of the cloud structure, and its coupling with dynamical systems like the Great Red Spot, are also becoming clearer, allowing speculation about their nature and origins. Analyses of the full four-year data set, some of which is still to be acquired, will add further details of the meteorological behaviour of Jupiter's atmosphere.

Abstract:

In its first two years of operation since arrival at Jupiter in December 1995, the Near Infrared Mapping spectrometer (NIMS) on the Galileo orbiter spacecraft obtained extensive coverage of the planet, including detailed coverage of the north equatorial belt (NEB) 'hot spot' region and the Great Red Spot. We will present the current state of data analysis including recent results on the abundances and variability of several minor constituents (H2O, CH4, NH3, GeH4, CH3D and PH3) and the cloud structure and morphology. (C) 1999 COSPAR. Published by Elsevier Science Ltd.

Abstract:

This paper considers the rationale for the exploration of Saturn's atmosphere by the Cassini mission, taking account of the key scientific questions posed by the earlier investigation by Voyager, and the capabilities of the instrumentation making up the Cassini payload. While by no means all objectives can be addressed by this particular configuration, in particular without a Saturn entry probe, if everything goes according to plan important progress should be possible on a number of key objectives. (C) 1998 Elsevier Science Ltd. All rights reserved.