Prof. Patrick Irwin

Abstract:

Mars, one of the most Earth-like of the planets, is today a cold, dry and barren world. However, there is good evidence that it may have been much warmer and wetter in the past and perhaps even supported life. The public interest aroused by these findings and by recent studies of 'SNC' meteorites, believed to have come from Mars, with their claims of the evidence of ancient Martian life, has focused attention on the ambitious programme of Mars Exploration currently being undertaken by NASA and ESA and has provided additional impetus. Improved measurements of the conditions on Mars' surface and in its atmosphere are central to both agencies' plans, and current atmospheric missions are reviewed in this paper together with possible future designs.

Abstract:

The understanding of the composition and cloud structure has advanced greatly in the last few years and in particular was greatly improved upon following the highly successful Pioneer and Voyager missions to that planet. Recently the Galileo spacecraft has gone into orbit about Jupiter and its remote sensing instruments, including the Near Infrared Mapping Spectrometer (NIMS) and the Solid State Imager (SSI), have yielded exciting new details of the spatial and vertical structure of the Jovian clouds and volatiles. At the same time Galileo's entry probe has made the first ever in situ measurements of conditions in the atmosphere. Recent ground-based observations have also added to the body of evidence from which conditions in the Jovian atmosphere may be inferred. This paper aims to review the current understanding of the composition and cloud structure of Jupiter's atmosphere in the light of the new Galileo results and recent ground-based, and earth-orbiting telescope observations.

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.