2015/06/02 by P. D. Feldman, Michael F. A’Hearn, Jean‐Loup Bertaux +8 · 1 citation
Physics and Astronomy · Earth and Planetary Sciences · #Astro and Planetary Science #Atmospheric Ozone and Climate #Atomic and Molecular Physics
paper · pdf · doi:10.1051/0004-6361/201525925
openalex publication_date 2015/06/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Aims. The Alice far-ultraviolet spectrograph onboard Rosetta is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/ Churyumov-Gerasimenko and to determine their spatial distribution and evolution with time and heliocentric distance. Methods. Following orbit insertion in August 2014, Alice made observations of the inner coma above the limbs of the nucleus of the comet from cometocentric distances varying between 10 and 80 km. Depending on the position and orientation of the slit relative to the nucleus, emissions of atomic hydrogen and oxygen were initially detected. These emissions are spatially localized close to the nucleus and spatially variable with a strong enhancement above the comet’s neck at northern latitudes. Weaker emission from atomic carbon and CO were subsequently detected. Results. Analysis of the relative line intensities suggests photoelectron impact dissociation of H 2 O vapor as the source of the observed H i and O i emissions. The electrons are produced by photoionization of H 2 O. The observed C i emissions are also attributed to electron impact dissociation, of CO 2 , and their relative brightness to H i reflects the variation of CO 2 to H 2 O column abundance in the coma.