Altitude profiles of O₂ on Mars from SPICAM stellar occultations

Bill R. Sandel (1) , Hannes Gröller (1) , Roger V. Yelle (1) , T. Koskinen (1) , Nikole K. Lewis (2) , Jean-Loup Bertaux (3) , Franck Montmessin (3) , Eric Quémerais (4)

1 LPL - Lunar and Planetary Laboratory [Tucson]
2 EAPS - Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge]
3 PLANETO - LATMOS
4 HELIOS - LATMOS

We determine the first altitude profiles of O₂ in the important photochemical region below 120 km in the atmosphere of Mars by analyzing Mars Express/SPICAM ultraviolet observations of six occultations of stars by the atmosphere. Over the range of 90–130 km the altitude-averaged mixing ratio of O₂ relative to the major constituent CO₂ varies in space and time in the range of 3.1×10^-3 to 5.8×10^-3, with a mean value of 4.0×10^-3. This mean value exceeds by a factor of 3–4 those reported earlier for the lower atmosphere. However, some of the O₂ abundance and mixing ratio profiles determined here are similar to those measured by Viking in 1976 in the upper atmosphere.

Mots clés: atmosphere; Mars; Ultraviolet observations; Stellar occultations; Aeronomy; composition; Atmospheres

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

Bill R. Sandel, Hannes Gröller, Roger V. Yelle, T. Koskinen, Nikole K. Lewis, et al.. Altitude profiles of O₂ on Mars from SPICAM stellar occultations. Icarus, 2015, 252, pp.154-160. ⟨10.1016/j.icarus.2015.01.004⟩. ⟨hal-01109178⟩