Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance? U. Hincelin, V. Wakelam, F. Hersant, S. Guilloteau, J. C. Loison, P. Honvault and J. Troe A&A, 530 (2011) A61 Published online: 11 May 2011 DOI: 10.1051/0004-6361/201016328