A study of the Martian water vapor over Hellas using OMEGA and PFS aboard Mars Express

Thérèse Encrenaz (1, 2) , Thierry Fouchet (1, 2) , Riccardo Melchiorri (1, 2) , Pierre Drossart (1, 2) , Brigitte Gondet (3) , Yves Langevin (3) , Jean-Pierre Bibring (3) , François Forget (4) , Luca Maltagliati (5) , Dmitry V. Titov (5) , Vittorio Formisano (6)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 Pôle Planétologie du LESIA
3 IAS - Institut d'astrophysique spatiale
4 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
5 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
6 IFSI - Istituto di Fisica dello Spazio Interplanetario

We used the OMEGA imaging spectrometer aboard Mars Express to study the evolution of the water vapor abundance over the Hellas basin, as a function of the seasonal cycle. The H2O column density is found to range from very low values (between southern fall and winter) up to more than 15 pr-mum during southern spring and summer. The general behavior is consistent with the expected seasonal cycle of water vapor on Mars, as previously observed by TES and modeled. In particular, the maximum water vapor content is observed around the southern solstice, and is significantly less than its northern couterpart. However, there is a noticeable discrepancy around the northern spring equinox (L_s = 330-60°), where the observed H2O column densities are significantly lower than the values predicted by the GCM. Our data show an abrupt enhancement of the water vapor column density (from 3 to 16 pr-mum) on a timescale of 3 days, for L_s = 251-254°. Such an increase, not predicted by the GCM, was also occasionally observed by TES over Hellas during previous martian years at the same season; however, its origin remains to be understood.

Domaines: Astrophysique [astro-ph]

Thérèse Encrenaz, Thierry Fouchet, Riccardo Melchiorri, Pierre Drossart, Brigitte Gondet, et al.. A study of the Martian water vapor over Hellas using OMEGA and PFS aboard Mars Express. Astronomy and Astrophysics - A&A, 2008, 484, pp.547-553. ⟨10.1051/0004-6361:20079288⟩. ⟨hal-03786490⟩