A study of the Martian water vapor over Hellas using OMEGA and PFS aboard Mars Express T. Encrenaz, T. Fouchet, R. Melchiorri, P. Drossart, B. Gondet, Y. Langevin, J.-P. Bibring, F. Forget, L. Maltagliati, D. Titov and V. Formisano A&A, 484 2 (2008) 547-553 Published online: 26 March 2008 DOI: 10.1051/0004-6361:20079288