Abstract :
The understanding of the composition and cloudstructure has advanced greatly in the last few yearsand in particular was greatly improved upon followingthe highly successful Pioneer and Voyager missions tothat planet. Recently the Galileo spacecraft has goneinto orbit about Jupiter and its remote sensinginstruments, including the Near Infrared MappingSpectrometer (NIMS) and the Solid State Imager (SSI),have yielded exciting new details of the spatial andvertical structure of the Jovian clouds and volatiles.At the same time Galileoʹs entry probe has made thefirst ever in situ measurements of conditions inthe atmosphere. Recent ground-based observations havealso added to the body of evidence from whichconditions in the Jovian atmosphere may be inferred.This paper aims to review the current understanding ofthe composition and cloud structure of Jupiterʹsatmosphere in the light of the new Galileo results andrecent ground-based, and earth-orbiting telescopeobservations.