Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko
Combi, M. R.
De Keyser, J.
Fuselier, S. A.
Gombosi, T. I.
Hansen, K. C.
Le Roy, L.
AffiliationUniv Arizona, Lunar & Planetary Lab
space vehicles: instruments
comets: individual: 67P/Churyumov-Gerasimenko
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationDirect Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko 2016, 462 (Suppl 1):S156 Monthly Notices of the Royal Astronomical Society
Rights© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
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AbstractWe analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double Focusing Mass Spectrometer data between 2014 August and 2016 February to examine the effect of seasonal variations on the four major species within the coma of 67P/Churyumov-Gerasimenko (H2O, CO2, CO, and O-2), resulting from the tilt in the orientation of the comet's spin axis. Using a numerical data inversion, we derive the non-uniform activity distribution at the surface of the nucleus for these species, suggesting that the activity distribution at the surface of the nucleus has not significantly been changed and that the differences observed in the coma are solely due to the variations in illumination conditions. A three-dimensional Direct Simulation Monte Carlo model is applied where the boundary conditions are computed with a coupling of the surface activity distributions and the local illumination. The model is able to reproduce the evolution of the densities observed by ROSINA including the changes happening at equinox. While O-2 stays correlated with H2O as it was before equinox, CO2 and CO, which had a poor correlation with respect to H2O pre-equinox, also became well correlated with H2O post-equinox. The integration of the densities from the model along the line of sight results in column densities directly comparable to the VIRTIS-H observations. Also, the evolution of the volatiles' production rates is derived from the coma model showing a steepening in the production rate curves after equinox. The model/data comparison suggests that the seasonal effects result in the Northern hemisphere of 67P's nucleus being more processed with a layered structure while the Southern hemisphere constantly exposes new material.
VersionFinal published version
SponsorsUS Rosetta Project [JPL1266313, JPL 1266314]; NASA [NNX14AG84G]; State of Bern; Swiss National Science Foundation; European Space Agency PRODEX; Jet Propulsion Laboratory ; Additional Researchers Grant; Fonds de la Recherche Scientifique [PDR T.1073.14]; ASI, Italy; CNES, France; DLR, Germany; NASA, USA; Belgian Science Policy Office [PRODEX/ROSINA PEA C4000107705]