| Description |
Water is ubiquitous in the Solar System, being present in gaseous form
in all planetary and cometary atmospheres, as ice on the surface and
subsurface of Mars, comets, most planetary satellites and distant bodies,
and in the liquid phase on Earth. Water plays an important or dominant
role in the chemistry of planetary and cometary atmospheres. Comets are
sources of water for planets through episodic collisions and continuous
production of ice-dust grains. This proposal addresses the broad topic
of water and its isotopologues in planetary and cometary atmospheres.
The nature of cometary activity and the thermodynamics of cometary
comae will be investigated by studying water excitation in a sample of
comets. The D/H ratio, the key for constraining the origin and evolution
of Solar System species, will be measured for the first time in a Jupiter-
family comet. A comparison with existing and new measurements of
D/H in Oort-cloud comets will constrain the composition of pre-solar
cometary grains and possibly the dynamics of the protosolar nebula.
New measurements of D/H in Giant Planets, similarly constraining the
composition of proto-planetary ices, will be obtained. The D/H and
other isotopic ratios, diagnostic of Mars atmosphere evolution, will be
accurately measured in H2O and CO. The role of water vapor in Mars
atmospheric chemistry will be studied by monitoring vertical profiles
of H2O and HDO and by searching for several other species. A detailed
study of the source of water in the upper atmosphere of the Giant Planets
and Titan will be performed. By monitoring the water abundance, vertical
profile, and input fluxes in the various objects, and when possible with
the help of mapping observations, we will discriminate between the
possible sources of water in the outer planets (interplanetary dust
particles, cometary impacts, and local sources). In addition to these
inter-connected objectives, serendipitous searches will enhance our
knowledge of the composition of planetary and cometary atmospheres. |
