The nature of Mars’s surface hydration: converging views from satellite (MEX), surface (MSL) and meteorite (NWA 7034 / 7533 and co) observations.

Friday, 19 December 2014: 5:00 PM
Pierre Beck1, Antoine Pommerol2, Brigitte Zanda3, Laurent Remusat4, Jean-Pierre Lorand5, Christa H Gopel6, Roger Hewins4,7, Sylvain Pont4, Eric Lewin8, Eric Quirico1, Bernard Schmitt1, German Montes-Hernandez8, Alexandre Garenne1, Lydie Bonal1, Olivier Proux9, Jean-Louis Hazemann10, Vincent Chevrier11, Javier Martín-Torres12, Maria-Paz Zorzano12, Olivier Gasnault13, Sylvestre Maurice14 and Roger C Wiens15, (1)UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Grenoble, France, (2)University of Bern, Bern, Switzerland, (3)Museum National d'Histoire Naturelle, paris, France, (4)Muséum National d´Histoire Naturelle, Laboratoire de Minéralogie et Cosmochimie du Muséum, Paris, France, (5)LPGN Laboratoire de Planétologie et Géodynamique de Nantes, Nantes Cedex 03, France, (6)Institut de Physique du Globe de Paris, Paris, France, (7)Rutgers University, Department of Earth and Planetary Sciences, Puscataway, NJ, United States, (8)UJF-Grenoble 1 / CNRS-INSU, Institut des Sciences de la Terre (IsTERRE), Grenoble, France, (9)Observatoire des Sciences de l’Univers de Grenoble (OSUG), Grenoble, France, (10)Institut Néel, Grenoble, France, (11)University of Arkansas, Fayetteville, AR, United States, (12)Centro de Astrobiologia, Madrid, Spain, (13)Universite de Toulouse, Toulouse Cedex 4, France, (14)IRAP, Toulouse, France, (15)Space Science and Applications, Los Alamos, NM, United States
Early infrared observations of the Martian surface have revealed the presence of a deep absorption between 2.6 and 3.5 µm usually referred to as the 3-µm band. Two non-exclusive explanations have been formulated to account for this 3-µm band. The first possibility is that it relates to the presence of some amount of adsorbed atmospheric water, water that would be exchangeable and could play a role in present day Mars water cycle. The alternative is that this absorption is due to an –OH or H2O bearing mineral component within the Martian dust, which would imply that water is involved at some stage of the dust production mechanism. Several lines of evidences seem to converge toward the second hypothesis.

First, after 10 years of mapping of the martian surface with OMEGA (MEX), the lack of variation of the 3-µm feature with surface relative humidity suggests that the surface hydration does not exchange with the atmosphere. This is in agreement with laboratory adsorption experiments under Mars conditions.

More recently the Mars Science Laboratory with unprecedented payload has provided some crucial constraints on the nature of surface hydration. The ChemCam instrument onboard MSL has detected hydrogen in dust and soil, and revealed the lack of variation of H concentration with surface humidity, including nighttime measurements. Also, evolved gas analysis by SAM of Gale crater soils shows that water is released at relatively high-temperature and suggest that –OH or H2O bearing phases are trapped in the amorphous component of soils.

Finally, the exceptional “black beauty” meteorite might also provide clues to the nature of Mars’s surface hydration. This Martian breccia shows elevated amount of water with respect to any other Martian meteorite. By studying the spectral properties of NWA 7533, we were able to show the presence of a 3-µm band and a small red-slope; this Martian breccia seems to contain a fine-oxidized-H-bearing component, possibly similar to that present in the Martian dust.