Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Water, Formation and Photodissociation

Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_5277-1




Water vapor can be formed in gas phase and on the ice mantles of dust grains (see “ Water in the Universe”). Once formed, the molecule is mainly destroyed by photodissociation through the effect of UV photons. In gas phase the molecule can be formed in low-temperature clouds through the chain of reactions:
$$ {\mathrm{H}}^{+}+\mathrm{O}\to \mathrm{H}+{\mathrm{O}}^{+}{\mathrm{H}}_2+{\mathrm{O}}^{+}\to \mathrm{O}{\mathrm{H}}^{+}+\mathrm{H}{\mathrm{H}}_3^{+}+\mathrm{O}\to \mathrm{O}{\mathrm{H}}^{+}+{\mathrm{H}}_2/{\mathrm{H}}_2{\mathrm{O}}^{+}+\mathrm{H}\mathrm{O}{\mathrm{H}}^{+}+{\mathrm{H}}_2\to {\mathrm{H}}_2{\mathrm{O}}^{+}+\mathrm{H}{\mathrm{H}}_2{\mathrm{O}}^{+}+{\mathrm{H}}_2\to {\mathrm{H}}_3{\mathrm{O}}^{+}+\mathrm{H}{\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{e}}^{\hbox{--}}\to {\mathrm{H}}_2\mathrm{O}+\mathrm{H}/\mathrm{O}\mathrm{H}+{\mathrm{H}}_2 $$


Water Vapor Chemical Process Electronic State Bioorganic Chemistry Interstellar Medium 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This is a preview of subscription content, log in to check access


  1. van Dishoeck EF, Herbst E, Neufeld DA (2013) Interstellar water chemistry: from laboratory to observations. Chem Rev 113:9045–9085Google Scholar
  2. van Dishoeck EF, Bergin EA, Lis DC, Lunine JI (2014) Water: from clouds to planets. In: Beuther H, Klessen R, Dullemond C, Henning T (eds) Protostars and planets VI. University of Arizona Press, Tucson, in pressGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Department of AstrophysicsLaboratory of Molecular AstrophysicsIorrejón de Ardoz, MadridSpain