| Description |
Water is ubiquitous in the Solar System, being present in gaseous formin all planetary and cometary atmospheres, as ice on the surface andsubsurface of Mars, comets, most planetary satellites and distant bodies,and in the liquid phase on Earth. Water plays an important or dominantrole in the chemistry of planetary and cometary atmospheres. Comets aresources of water for planets through episodic collisions and continuousproduction of ice-dust grains. This proposal addresses the broad topicof water and its isotopologues in planetary and cometary atmospheres.The nature of cometary activity and the thermodynamics of cometarycomae will be investigated by studying water excitation in a sample ofcomets. The D/H ratio, the key for constraining the origin and evolutionof Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements ofD/H in Oort-cloud comets will constrain the composition of pre-solarcometary grains and possibly the dynamics of the protosolar nebula.New measurements of D/H in Giant Planets, similarly constraining thecomposition of proto-planetary ices, will be obtained. The D/H andother isotopic ratios, diagnostic of Mars. atmosphere evolution, will beaccurately measured in H2O and CO. The role of water vapor in Mars.atmospheric chemistry will be studied by monitoring vertical profilesof H2O and HDO and by searching for several other species. A detailedstudy of the source of water in the upper atmosphere of the Giant Planetsand Titan will be performed. By monitoring the water abundance, verticalprofile, and input fluxes in the various objects, and when possible withthe help of mapping observations, we will discriminate between thepossible sources of water in the outer planets (interplanetary dustparticles, cometary impacts, and local sources). In addition to theseinter-connected objectives, serendipitous searches will enhance ourknowledge of the composition of planetary and cometary atmospheres. |
