Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko

the VIRTIS and the ROSINA teams

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double FocusingMass 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 O2), 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.Athree-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 ROSINAincluding the changes happening at equinox. While O2 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.

Original languageEnglish (US)
Pages (from-to)S156-S169
JournalMonthly Notices of the Royal Astronomical Society
Volume462
DOIs
StatePublished - 2016

Fingerprint

coma
comets
comet
modeling
simulation
nuclei
spectrometer
illumination
spectrometers
data inversion
Southern Hemisphere
Northern Hemisphere
annual variations
guy wires
tilt
line of sight
boundary condition
seasonal variation
inversions
boundary conditions

Keywords

  • Comets: general
  • Comets: individual: 67P/Churyumov-Gerasimenko
  • Space vehicles
  • Space vehicles: instruments

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko. / the VIRTIS and the ROSINA teams.

In: Monthly Notices of the Royal Astronomical Society, Vol. 462, 2016, p. S156-S169.

Research output: Contribution to journalArticle

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title = "Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko",
abstract = "We analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double FocusingMass 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 O2), 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.Athree-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 ROSINAincluding the changes happening at equinox. While O2 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.",
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T1 - Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko

AU - the VIRTIS and the ROSINA teams

AU - Fougere, Nicolas

AU - Altwegg, K.

AU - Berthelier, J. J.

AU - Bieler, A.

AU - Bockelée-Morvan, D.

AU - Calmonte, U.

AU - Capaccioni, F.

AU - R. Combi, M.

AU - De Keyser, J.

AU - Debout, V.

AU - Erard, S.

AU - Fiethe, B.

AU - Filacchione, G.

AU - Fink, Uwe -

AU - Fuselier, S. A.

AU - Gombosi, T. I.

AU - Hansen, K. C.

AU - Hässig, M.

AU - Huang, Z.

AU - Le Roy, L.

AU - Leyrat, C.

AU - Migliorini, A.

AU - Piccioni, G.

AU - Rinaldi, G.

AU - Rubin, M.

AU - Shou, Y.

AU - Tenishev, V.

AU - Toth, G.

AU - Tzou, C. Y.

PY - 2016

Y1 - 2016

N2 - We analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double FocusingMass 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 O2), 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.Athree-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 ROSINAincluding the changes happening at equinox. While O2 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.

AB - We analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double FocusingMass 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 O2), 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.Athree-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 ROSINAincluding the changes happening at equinox. While O2 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.

KW - Comets: general

KW - Comets: individual: 67P/Churyumov-Gerasimenko

KW - Space vehicles

KW - Space vehicles: instruments

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