Water: from clouds to planets
Results from recent space missions, in particular Spitzer and Herschel, have led to significant 
progress in our understanding of the formation and transport of water from clouds to disks, 
planetesimals, and planets. [n this review, we provide the underpinnings for the basic molecular 
physics and chemistry of water and outline these advances in the context of water formation 
in space, its transport to a forming disk, its evolution in the disk, and finally the delivery to 
forming terrestrial worlds and accretion by gas giants. Throughout, we pay close attention to 
the disposition of water as vapor or solid and whether it might be subject to processing at any 
stage. The context of the water in the solar system and the isotopic ratios (D/H) in various 
bodies are discussed as grounding data points for this evolution. Additional advances include 
growing knowledge of the composition of atmospheres of extrasolar gas giants, which may be 
influenced by the variable phases of water in the protoplanetary disk. Furthermore, the architecture 
of extrasolar systems leaves strong hints of dynamical interactions, which are important 
for the delivery of water and subsequent evolution of planetary systems. We conclude with 
an exploration of water on Earth and note that all the processes and key parameters identified 
here should also hold for exoplanetary systems.