Evolution of CO${}_2$, CH${}_4$, and OCS abundances relative to H${}_2$O in the coma of comet 67P around perihelion from Rosetta/VIRTIS-H observations

Abstract

Infrared observations of the coma of 67P/Churyumov-Gerasimenko were carried out from July to September 2015, i.e., around perihelion (13 August 2015), with the high-resolution channel of the VIRTIS instrument onboard Rosetta. We present the analysis of fluorescence emission lines of H${}_2$O, CO${}_2$, ${}^{13}$CO${}_2$, OCS, and CH${}_4$ detected in limb sounding with the field of view at 2.7-5 km from the comet centre. Measurements are sampling outgassing from the illuminated southern hemisphere, as revealed by H${}_2$O and CO${}_2$ raster maps, which show anisotropic distributions, aligned along the projected rotation axis. An abrupt increase of water production is observed six days after perihelion. In the mean time, CO${}_2$, CH${}_4$, and OCS abundances relative to water increased by a factor of 2 to reach mean values of 32%, 0.47%, and 0.18%, respectively, averaging post-perihelion data. We interpret these changes as resulting from the erosion of volatile-poor surface layers. Sustained dust ablation due to the sublimation of water ice maintained volatile-rich layers near the surface until at least the end of the considered period, as expected for low thermal inertia surface layers. The large abundance measured for CO${}_2$ should be representative of the 67P nucleus original composition, and indicates that 67P is a CO${}_2$-rich comet. Comparison with abundance ratios measured in the northern hemisphere shows that seasons play an important role in comet outgassing. The low CO${}_2$/H${}_2$O values measured above the illuminated northern hemisphere are not original, but the result of the devolatilization of the uppermost layers.

arXiv commentAccepted for publication in the Monthly Notices of the Royal Astronomical Society

References in corpus (9)

• A high accuracy computed water line list
• Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft
• Are fractured cliffs the source of cometary dust jets ? Insights from OSIRIS/Rosetta at 67P
• The Composition of Comets
• Measurements of the Near-Nucleus Coma of Comet 67P/Churyumov-Gerasimenko with the Alice Far-Ultraviolet Spectrograph on Rosetta
• The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. I) Prelanding mission phase
• Evolution of H${}_2$O, CO, and CO${}_2$ Production in Comet C/2009 P1 Garradd During the 2011-2012 Apparition
• How to link the relative abundances of gas species in coma of comets to their initial chemical composition ?
• The CO2 Abundance in Comets C/2012 K1 (PanSTARRS), C/2012 K5 (LINEAR), and 290P/Jager as Measured with Spitzer

Cited by in corpus (27)

• Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko
• Ingredients for Solar-like Systems: protostar IRAS 16293-2422 B versus comet 67P/Churyumov-Gerasimenko
• The carbon monoxide-rich interstellar comet 2I/Borisov
• The Surface Distributions of the Production of the Major Volatile Species, H2O, CO2, CO and O2, from the Nucleus of Comet 67P/Churyumov-Gerasimenko throughout the Rosetta Mission as Measured by the ROSINA Double Focusing Mass Spectrometer
• The gas production of 14 species from comet 67P/Churyumov-Gerasimenko based on DFMS/COPS data from 2014-2016
• Comet 67P outbursts and quiescent coma at 1.3 AU from the Sun: dust properties from Rosetta/VIRTIS-H observations
• Surface localization of gas sources on comet 67P/Churyumov-Gerasimenko based on DFMS/COPS data
• The dust-to-gas ratio, size distribution, and dust fall-back fraction of comet 67P/Churyumov-Gerasimenko: Inferences from linking the optical and dynamical properties of the inner comae
• The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission
• Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko
• H${}_2$O and O${}_2$ Absorption in the Coma of Comet 67P/Churyumov-Gerasimenko Measured by the Alice Far-Ultraviolet Spectrograph on Rosetta
• Importance of tunneling in H-abstraction reactions by OH radicals: The case of CH4 + OH studied through isotope-substituted analogs
• VIRTIS-H observations of comet 67P's dust coma: spectral properties and color temperature variability with phase and elevation
• FUV Spectral Signatures of Molecules and the Evolution of the Gaseous Coma of Comet 67P/Churyumov-Gerasimenko
• Ultraviolet Observations of Coronal Mass Ejection Impact on Comet 67P/Churyumov-Gerasimenko by Rosetta Alice
• Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta
• High-resolution optical spectroscopic observations of comet 21P/Giacobini-Zinner in Its 2018 apparition
• Water Ortho-to-Para ratio in the coma of comet 67P/Churyumov-Gerasimenko
• The ice composition close to the surface of comet 67P/Churyumov-Gerasimenko
• Multi-instrument analysis of far-ultraviolet aurora in the southern hemisphere of comet 67P/Churyumov-Gerasimenko
• HSCO${}^{+}$ and DSCO${}^{+}$: a multi-technique approach in the laboratory for the spectroscopy of interstellar ions
• Stellar Occultation by Comet 67P/Churyumov-Gerasimenko Observed with Rosetta's Alice Far-Ultraviolet Spectrograph
• Advancing spectroscopic understanding of HOCS${}^{+}$: Laboratory investigations and astronomical implications
• A link between the size and composition of comets
• Upper Limits for Emissions in the Coma of Comet 67P/Churyumov-Gerasimenko Near Perihelion as Measured by Rosetta's Alice Far-Ultraviolet Spectrograph
• Spatial Distribution of Ultraviolet Emission from Cometary Activity at 67P/Churyumov-Gerasimenko
• Carbon dioxide clathrate hydrate formation at low temperature. Diffusion-limited kinetics growth as monitored by FTIR