Photochemistry of O(1D) and O(1S) lines in the coma of 67P/Churyumov-Gerasimenko

Gaël Cessateur , Johan de Keyser , Romain Maggiolo , Andrew Gibbons , Guillaume Gronoff , Herbert Gunell , Frederik Dhooghe , Jérôme Loreau , Nathalie Vaeck , Kathrin Altwegg , Andre Bieler , Christelle Briois (1) , Ursina Calmonte , Michael Combi , Stephen Fuselier , Tamas Gombosi , Myrtha Haessig , Lena Le Roy , Eddy Neefs , Martin Rubin

1 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

We present here a chemistry-emission coupled model to study the production and loss mechanisms of the O(1D) and O(1S) states, for comet 67P/Churyumov-Gerasimenko. The recent discovery of O2 in significant abundance relative to water (3.80% +/- 0.85%, Bieler et al. 2015) within the coma of 67P has been taken into consideration for the first time in such models. We evaluate the effect of the presence of O2 on the green to red-doublet emission intensity ratio, which is traditionally used to assess the CO2 abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O2 into account leads to an underestimation of the CO2 abundance within 67P. This strongly suggests that the green to red-doublet emission intensity ratio alone is not a proper tool for determining the CO2 abundance, as previously suggested. O2 might indeed be a rather common and abundant parent species, following the re-analysis of the comet 1P/Halley data (Rubin et al. 2015). Therefore, it is likely that earlier determinations of the CO2 abundance in cometary atmospheres have to be revisited.

Domains: Sciences of the Universe [physics]

Gaël Cessateur, Johan de Keyser, Romain Maggiolo, Andrew Gibbons, Guillaume Gronoff, et al.. Photochemistry of O(1D) and O(1S) lines in the coma of 67P/Churyumov-Gerasimenko. EGU General Assembly 2016, Apr 2016, Vienne, Austria. ⟨insu-03573511⟩