Search

Your search keyword '"Fougere, Nicolas"' showing total 29 results
Start Over Author "Fougere, Nicolas"

Refine your results

more »

more »

more »

more »
29 results on '"Fougere, Nicolas"'

1. 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

Author

Combi, Michael, Shou, Yinsi, Fougere, Nicolas, Tenishev, Valeriy, Altwegg, Kathrin, Rubin, Martin, Bockelée-Morvan, Dominique, Capaccioni, Fabrizio, Cheng, Yu-Chi, Fink, Uwe, Gombosi, Tamas, Hansen, Kenneth C., Huang, Zhenguang, Marshall, David, and Toth, Gabor

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) suite of instruments operated throughout the over two years of the Rosetta mission operations in the vicinity of comet 67P/Churyumov-Gerasimenko. It measured gas densities and composition throughout the comet's atmosphere, or coma. Here we present two-years' worth of measurements of the relative densities of the four major volatile species in the coma of the comet, H2O. CO2, CO and O2, by one of the ROSINA sub-systems called the Double Focusing Mass Spectrometer (DFMS). The absolute total gas densities were provided by the Comet Pressure Sensor (COPS), another ROSINA sub-system. DFMS is a very high mass resolution and high sensitivity mass spectrometer able to resolve at a tiny fraction of an atomic mass unit. We have analyzed the combined DFMS and COPS measurements using an inversion scheme based on spherical harmonics that solves for the distribution of potential surface activity of each species as the comet rotates, changing solar illumination, over short intervals and as the comet changes distance from the sun and orientation of its spin axis over long time intervals. We also use the surface boundary conditions derived from the inversion scheme to simulate the whole coma with our fully kinetic Direct Simulation Monte Carlo model and calculate the production rates of the four major species throughout the mission. We compare the derived production rates with revised remote sensing observations by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) as well as with published observations from the Microwave Instrument for the Rosetta Orbiter (MIRO). Finally we use the variation of the surface production of the major species to calculate the total mass loss over the mission and, for different estimates of the dust/gas ratio, calculate the variation of surface loss over the nucleus., Comment: 144 pages, 9 figures, 8 tables, 1 supplemental table

Published
2019
Full Text
View/download PDF

2. Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles

Author

Blum, Jürgen, Gundlach, Bastian, Krause, Maya, Fulle, Marco, Johansen, Anders, Agarwal, Jessica, von Borstel, Ingo, Shi, Xian, Hu, Xuanyu, Bentley, Mark S., Capaccioni, Fabrizio, Colangeli, Luigi, Della Corte, Vincenzo, Fougere, Nicolas, Green, Simon F., Ivanovski, Stavro, Mannel, Thurid, Merouane, Sihane, Migliorini, Alessandra, Rotundi, Alessandra, Schmied, Roland, and Snodgrass, Colin

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The processes that led to the formation of the planetary bodies in the Solar System are still not fully understood. Using the results obtained with the comprehensive suite of instruments on-board ESA's Rosetta mission, we present evidence that comet 67P/Churyumov-Gerasimenko likely formed through the gentle gravitational collapse of a bound clump of mm-sized dust aggregates ("pebbles"), intermixed with microscopic ice particles. This formation scenario leads to a cometary make-up that is simultaneously compatible with the global porosity, homogeneity, tensile strength, thermal inertia, vertical temperature profiles, sizes and porosities of emitted dust, and the steep increase in water-vapour production rate with decreasing heliocentric distance, measured by the instruments on-board the Rosetta spacecraft and the Philae lander. Our findings suggest that the pebbles observed to be abundant in protoplanetary discs around young stars provide the building material for comets and other minor bodies., Comment: accepted by MNRAS

Published
2017
Full Text
View/download PDF

6. Probing the Evolutionary History of Comets: an Investigation of the Hypervolatiles CO, CH4, and C2H6 in the Jupiter-Family Comet 21P/Giacobini–Zinner

Author

Roth, Nathan X, Gibb, Erika L, Bonev, Boncho P, DiSanti, Michael A, Russo, Neil Dello, McKay, Adam J, Vervack, Ronald J., Jr, Kawakita, Hideyo, Saki, Mohammad, Biver, Nicolas, Bockelée-Morvan, Dominique, Feaga, Lori M, Fougere, Nicolas, Cochran, Anita L, Combi, Michael, and Shou, Yinsi

Subjects
Space Sciences (General)
Abstract

Understanding the cosmogonic record encoded in the parent volatiles stored in cometary nuclei requires investigating whether evolution (thermal or otherwise) has modified the composition of short-period comets during successive perihelion passages. As the most volatile molecules systematically observed in comets, the abundances of CO, CH4, and C2H6 in short-period comets may serve to elucidate the interplay between natal conditions and post-formative evolution in setting present-day composition, yet secure measurements of CO and CH4 in Jupiter-family comets (JFCs) are especially sparse. The highly favorable 2018 apparition of JFC 21P/Giacobini–Zinner enabled a sensitive search for these "hypervolatiles" in a prototypical carbon-chain depleted comet. We observed 21P/Giacobini–Zinner with the iSHELL spectrograph at the NASA Infrared Telescope Facility on four pre-perihelion dates, two dates near-perihelion, and one post-perihelion date. We obtained detections of CO, CH4, and C2H6 simultaneously with H2O on multiple dates. We present rotational temperatures, production rates, and mixing ratios. Combined with previous work, our results may indicate that the hypervolatile coma composition of 21P/Giacobini–Zinner was variable across apparitions as well as within a particular perihelion passage, yet the spread in these measurements is a relatively small fraction of the variation in each molecule from comet to comet. We discuss the implications of our measured hypervolatile content of 21P/Giacobini–Zinner for the evolution of JFCs, and place our results in the context of findings from the Rosetta mission and ground-based studies of comets.

Published
2020
Full Text
View/download PDF

7. Testing Short-term Variability and Sampling of Primary Volatiles in Comet 46P/Wirtanen

Author

Khan, Younas, primary, Gibb, Erika L., additional, Bonev, Boncho P., additional, Roth, Nathan X., additional, Saki, Mohammad, additional, DiSanti, Michael A., additional, Russo, Neil Dello, additional, Vervack, Ronald J., additional, McKay, Adam J., additional, Combi, Michael R., additional, Shou, Yinsi, additional, Cordiner, Martin A., additional, Kawakita, Hideyo, additional, Fougere, Nicolas, additional, and Protopapa, Silvia, additional

Published
2021
Full Text
View/download PDF

9. Lyα Observations of Comet C/2013 A1 (Siding Spring) Using MAVEN IUVS Echelle

Author

Mayyasi, Majd, primary, Clarke, John, additional, Combi, Michael, additional, Fougere, Nicolas, additional, Quemerais, Eric, additional, Katushkina, Olga, additional, Bhattacharyya, Dolon, additional, Crismani, Matteo, additional, Deighan, Justin, additional, Jain, Sonal, additional, Schneider, Nicholas, additional, and Jakosky, Bruce, additional

Published
2020
Full Text
View/download PDF

10. 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

Author

Combi, Michael, primary, Shou, Yinsi, additional, Fougere, Nicolas, additional, Tenishev, Valeriy, additional, Altwegg, Kathrin, additional, Rubin, Martin, additional, Bockelée-Morvan, Dominique, additional, Capaccioni, Fabrizio, additional, Cheng, Yu-Chi, additional, Fink, Uwe, additional, Gombosi, Tamas, additional, Hansen, Kenneth C., additional, Huang, Zhenguang, additional, Marshall, David, additional, and Toth, Gabor, additional

Published
2020
Full Text
View/download PDF

11. Relationship between inner coma water emissions and ice deposits in comet 67P/Churyumov-Gerasimenko

Author

MIGLIORINI, Alessandra, FILACCHIONE, GIANRICO, DE SANCTIS, MARIA CRISTINA, CAPACCIONI, FABRIZIO, PICCIONI, GIUSEPPE, Bockelée-Morvan, Dominique, Erard, Stephane, Leyrat, Cedric, CIARNIELLO, Mauro, Combi, Michael, Fougere, Nicolas, and Taylor, Fred

Abstract

Data acquired in April 2015 with the VIRTIS spectrometer on board the Rosetta mission provided information on the possible correlation between the H2O emission in the inner coma and the exposed water deposits detected in the Hapi region on the 67P/Churyumov-Gerasimenko surface (Migliorini et al. submitted). Further bright spots attributed to exposed water ice have been identified in other regions by OSIRIS at visible wavelengths (Pommerol, et al., 2015) and confirmed in the infrared by VIRTIS-M in the Imothep region (Filacchione et al., 2016). Furthermore, new water ice deposits have been identified in regions located both at the equator and at southern latitudes. These regions might be localised sources of water emissions in the inner coma of 67P/C-G. The present investigation seeks to identify the spatial and temporal correlations between the H2O emissions in the inner coma and the water ice rich deposits on the surface in order to identify the mechanisms operating at the surface-coma interface. It extends the study already carried out for a limited region located in the comet's neck, and identifies how the observed emissions and deposits evolve with the heliocentric distance, as observed by VIRTIS during the Rosetta escort phase mission.

Published
2016

12. Investigating the correlations between water coma emissions and active regions in comet 67P/ Churyumov-Gerasimenko

Author

MIGLIORINI, Alessandra, FILACCHIONE, GIANRICO, CAPACCIONI, FABRIZIO, PICCIONI, GIUSEPPE, Bockelee-Morvan, Dominique, Érard, Stéphane, Leyrat, Cedric, Combi, Michael R., Fougere, Nicolas, RINALDI, GIOVANNA, and VIRTIS Team

Abstract

Vibrational emission lines of H2O and CO2 at 2.67 and 4.27 μm, respectively, were identified by the VIRTIS spectrometer (Bockelée-Morvan et al., 2015; Migliorini et al., 2016; Fink et al., 2016) and mapped from the surface up to about 10 km altitude with a spatial resolution on the order of tens of meters per pixel (Migliorini et al., 2016).Data acquired in April 2015 with the VIRTIS spectrometer on board the Rosetta mission, provided information on the possible correlation between the H2O emission in the inner coma and the exposed water deposits detected in the Hapi region on the 67P/Churyumov-Gerasimenko surface (Migliorini et al., 2106; De Sanctis et al., 2015). Further bright spots attributed to exposed water ice have been identified in other regions by OSIRIS at visible wavelengths (Pommerol, et al., 2015) and confirmed in the infrared by VIRTIS-M in the Imothep region (Filacchione et al., 2016). The small dimensions of these icy spots - approximately 100x100 m (Filacchione et al., 2016) - and the relatively small amount of water ice (about 5%) make uncertain the correlation with the strong emissions in the coma.However, VIRTIS data show that the distribution of jet-like emissions seems to follow the distribution of cliffs and exposed areas identified in the North hemisphere with OSIRIS camera (Vincent et al., 2015). These areas are mainly concentrated in correspondence of comet's rough terrains, while a lack of active regions is observed in the comet's neck. Nevertheless, strong H2O emission is observed above the neck with VIRTIS. This might be a consequence of gas jets that are originated in the surrounding of the neck but converging towards the neck itself. This gaseous activity is the main driver of the dust upwelling (Migliorini et al, 2016; Rinaldi et al., in preparation)In this paper, we investigate the relationship between H2O vapour observed with VIRTIS within 5 km from the 67P/C-G nucleus and the exposed regions identified by OSIRIS on the surface (in the timeframe March to April 2015) with an attempt to address possible variations with the heliocentric distance.

Published
2016

13. Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles

Author

Blum, Jürgen, primary, Gundlach, Bastian, additional, Krause, Maya, additional, Fulle, Marco, additional, Johansen, Anders, additional, Agarwal, Jessica, additional, von Borstel, Ingo, additional, Shi, Xian, additional, Hu, Xuanyu, additional, Bentley, Mark S, additional, Capaccioni, Fabrizio, additional, Colangeli, Luigi, additional, Della Corte, Vincenzo, additional, Fougere, Nicolas, additional, Green, Simon F, additional, Ivanovski, Stavro, additional, Mannel, Thurid, additional, Merouane, Sihane, additional, Migliorini, Alessandra, additional, Rotundi, Alessandra, additional, Schmied, Roland, additional, and Snodgrass, Colin, additional

Published
2017
Full Text
View/download PDF

14. Modeling of the Inner Coma of Comet 67P/Churyumov-Gerasimenko Constrained by VIRTIS and ROSINA Observations

Author

Fougere, Nicolas, Combi, Michael, Tenishev, Valeriy, Bieler, André, Migliorini, Alessandra, Bockelée-Morvan, Dominique, Toth, Gabor, Huang, Zhenguang, Gombosi, Tamas I., Hansen, Kenneth, Capaccioni, Fabrizio, Filacchione, Gianrico, Piccioni, Giuseppe, Debout, Vincent, Erard, Stéphane, Leyrat, Cedric, Fink, Uwe, Rubin, Martin, Altwegg, Kathrin, Tzou, Chia-yu, Le Roy, Léna, Calmonte, Ursina, Berthelier, Jean-Jacques, Rème, Henri, Hässig, Myrtha, Fuselier, Stephen, Fiethe, Björn, De Keyser, Johan, Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Physikalisches Institut [Bern], Universität Bern [Bern] (UNIBE), Center for Space and Habitability (CSH), University of Bern, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Space Science Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Institute of Computer and Network Engineering [Braunschweig] (IDA), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Universität Bern [Bern], Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), IMPEC - LATMOS, Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Technische Universität Braunschweig [Braunschweig], Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] ( AOSS ), Istituto di Astrofisica e Planetologia Spaziali ( IAPS ), Istituto Nazionale di Astrofisica ( INAF ), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Lunar and Planetary Laboratory [Tucson], Center for Space and Habitability ( CSH ), Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Southwest Research Institute [San Antonio] ( SwRI ), Institute of Computer and Network Engineering [Braunschweig] ( IDA ), and Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique ( BIRA-IASB )

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [ SDU.ASTR.IM ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [ SDU.ASTR.SR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; As it orbits around comet 67P/Churyumov-Gerasimenko (CG), the Rosetta spacecraft acquires more information about its main target. The numerous observations made at various geometries and at different times enable a good spatial and temporal coverage of the evolution of CG’s cometary coma. However, the question regarding the link between the coma measurements and the nucleus activity remains relatively open notably due to gas expansion and strong kinetic effects in the comet’s rarefied atmosphere.In this work, we use coma observations made by the ROSINA-DFMS instrument to constrain the activity at the surface of the nucleus. The distribution of the H2O and CO2 outgassing is described with the use of spherical harmonics. The coordinates in the orthogonal system represented by the spherical harmonics are computed using a least squared method, minimizing the sum of the square residuals between an analytical coma model and the DFMS data.Then, the previously deduced activity distributions are used in a Direct Simulation Monte Carlo (DSMC) model to compute a full description of the H2O and CO2 coma of comet CG from the nucleus’ surface up to several hundreds of kilometers. The DSMC outputs are used to create synthetic images, which can be directly compared with VIRTIS measurements.The good agreement between the VIRTIS observations and the DSMC model, itself constrained with ROSINA data, provides a compelling juxtaposition of the measurements from these two instruments.

Published
2015

16. A 3D Description of the Coma of Comet 67P/Churyumov-Gerasimenko Constrained by Rosetta Observations

Author

Fougere, Nicolas, Tenishev, Valeriy, Bieler, Andre, Combi, Michael, Gombosi, Tamas, Hansen, Kenneth, Jia, Xianzhe, Shou, Yinsi, Huang, Zhenguang, Toth, Gabor, Altwegg, Kathrin, Wurz, Peter, Balsiger, Hans, Jäckel, Annette, Le Roy, Lena, Gasc, Sébastien, Calmonte, Ursina, Rubin, Martin, Tzou, Chia-Yu, Hässig, Myrtha, Fuselier, Stephen, Johan De Keyser, Berthelier, Jean-Jacques, Mall, Urs, Rème, Henri, Fiethe, Björn, Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] ( AOSS ), University of Michigan [Ann Arbor], Physikalisches Institut [Bern], Universität Bern [Bern], Space Science Division [San Antonio], Southwest Research Institute [San Antonio] ( SwRI ), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique ( BIRA-IASB ), IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Max Planck Institute for Solar System Research ( MPS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Institute of Computer and Network Engineering [Braunschweig] ( IDA ), Technische Universität Braunschweig [Braunschweig], Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan System-University of Michigan System, Southwest Research Institute [San Antonio] (SwRI), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institute of Computer and Network Engineering [Braunschweig] (IDA), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Universität Bern [Bern] (UNIBE), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

International audience; For the first time, the Rosetta spacecraft stays with a comet over an extended period of time during its journey in the inner the solar system. The data provided by the suite of instruments on board the Rosetta spacecraft, notably the ROSINA mass spectrometers and the pressure sensor, provides critical information concerning comet 67P/Churyumov-Gerasimenko (CG) and its environment. These measurements reinforce our knowledge of comet CG and enable us to describe the nucleus and the sources with more details. The observations allow us to better constrain and accordingly develop much more realistic models of the comet’s coma.We show a 3D simulation of the gas and dust coma of comet CG using a Direct Simulation Monte-Carlo model performed with the Adaptive Mesh Particle Simulator (Tenishev et al. 2008, 2011). The coma model presented includes a realistic nucleus shape, with a gas flux distribution and a surface temperature that takes into account irregularities and concavities of the nucleus. Along with the gas drag, the gravity field drives the dust dynamics and is therefore accurately computed around the irregular nucleus shape. This constitutes the state-of-the-art of cometary coma models, which are crucial to interpret instrument data and for further mission planning.Acknowledgement:This work was supported by contracts JPL#1266313 and JPL#1266314 from the US Rosetta Project and NASA grant NNX09AB59G from the Planetary Atmospheres Program.References:Tenishev et al. 2008 ApJ 685:659, and 2011 ApJ 732:104

Published
2014

17. 3D Direct Simulation Monte Carlo Modeling of the Spacecraft Environment of Rosetta

Author

Bieler, Andre, Tenishev, Valeriy, Fougere, Nicolas, Gombosi, Tamas, Hansen, Kenneth, Combi, Michael, Huang, Zhenguang, Jia, Xianzhe, Toth, Gabor, Altwegg, Kathrin, Wurz, Peter, Jäckel, Annette, Le Roy, Lena, Gasc, Sébastien, Calmonte, Ursina, Rubin, Martin, Tzou, Chia-Yu, Hässig, Myrtha, Fuselier, Stephen, Johan De Keyser, Berthelier, Jean-Jacques, Mall, Urs, Rème, Henri, Fiethe, Björn, Balsiger, Hans, Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Physikalisches Institut [Bern], Universität Bern [Bern], Space Science Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institute of Computer and Network Engineering [Braunschweig] (IDA), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] ( AOSS ), Southwest Research Institute [San Antonio] ( SwRI ), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique ( BIRA-IASB ), IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Max Planck Institute for Solar System Research ( MPS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Institute of Computer and Network Engineering [Braunschweig] ( IDA ), Technische Universität Braunschweig [Braunschweig], Universität Bern [Bern] (UNIBE), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics::Space Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [ SDU.ASTR.IM ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Astrophysics::Earth and Planetary Astrophysics, [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The European Space Agency’s Rosetta mission is the first to escort a comet over an extended time as the comet makes its way through the inner solar system. The ROSINA instrument suite consisting of a double focusing mass spectrometer, a time of flight mass spectrometer and a pressure sensor, will provide temporally and spatially resolved data on the comet’s volatile inventory.The effect of spacecraft outgassing is well known and has been measured with the ROSINA instruments onboard Rosetta throughout the cruise phase. The flux of released neutral gas originating from the spacecraft cannot be distinguished from the cometary signal by the mass spectrometers and varies significantly with solar illumination conditions. For accurate interpretation of the instrument data, a good understanding of spacecraft outgassing is necessary. In this talk we present results simulating the spacecraft environment with the Adaptive Mesh Particle Simulator (AMPS) code. AMPS is a direct simulation monte carlo code that includes multiple species in a 3D adaptive mesh to describe a full scale model of the spacecraft environment. We use the triangulated surface model of the spacecraft to implement realistic outgassing rates for different areas on the surface and take shadowing effects in consideration. The resulting particle fluxes are compared to the measurements of the ROSINA experiment and implications for ROSINA measurements and data analysis are discussed. Spacecraft outgassing has implications for future space missions to rarefied atmospheres as it imposes a limit on the detection of various species.

Published
2014

19. Four‐fluid MHD simulations of the plasma and neutral gas environment of comet 67P/Churyumov‐Gerasimenko near perihelion

Author

Huang, Zhenguang, primary, Tóth, Gábor, additional, Gombosi, Tamas I., additional, Jia, Xianzhe, additional, Rubin, Martin, additional, Fougere, Nicolas, additional, Tenishev, Valeriy, additional, Combi, Michael R., additional, Bieler, Andre, additional, Hansen, Kenneth C., additional, Shou, Yinsi, additional, and Altwegg, Kathrin, additional

Published
2016
Full Text
View/download PDF

20. Ultraviolet observations of the hydrogen coma of comet C/2013 A1 (Siding Spring) by MAVEN/IUVS

Author

Crismani, Matteo M. J., primary, Schneider, Nicholas M., additional, Deighan, Justin I., additional, Stewart, A. Ian F., additional, Combi, Michael, additional, Chaffin, Michael S., additional, Fougere, Nicolas, additional, Jain, Sonal K., additional, Stiepen, Arnaud, additional, Yelle, Roger V., additional, McClintock, William E., additional, Clarke, John T., additional, Holsclaw, Gregory M., additional, Montmessin, Frank, additional, and Jakosky, Bruce M., additional

Published
2015
Full Text
View/download PDF

21. Comparison of 3D kinetic and hydrodynamic models to ROSINA-COPS measurements of the neutral coma of 67P/Churyumov-Gerasimenko

Author

Bieler, Andre, primary, Altwegg, Kathrin, additional, Balsiger, Hans, additional, Berthelier, Jean-Jacques, additional, Calmonte, Ursina, additional, Combi, Michael, additional, De Keyser, Johan, additional, Fiethe, Björn, additional, Fougere, Nicolas, additional, Fuselier, Stephen, additional, Gasc, Sébastien, additional, Gombosi, Tamas, additional, Hansen, Kenneth, additional, Hässig, Myrtha, additional, Huang, Zhenguang, additional, Jäckel, Annette, additional, Jia, Xianzhe, additional, Le Roy, Lena, additional, Mall, Urs A., additional, Rème, Henri, additional, Rubin, Martin, additional, Tenishev, Valeriy, additional, Tóth, Gábor, additional, Tzou, Chia-Yu, additional, and Wurz, Peter, additional

Published
2015
Full Text
View/download PDF

22. Design of a low cost mission to the Neptunian system

Author

Alibay, Farah, primary, Fernandes, Philip, additional, McGranaghan, Ryan, additional, Leonard, Jason, additional, Clegg, Ryan, additional, Craig, Patricia, additional, Day, Mackenzie, additional, Fougere, Nicolas, additional, Girazian, Zachary, additional, Hosseini, Sona, additional, Hutchins, Michael, additional, Scully, Jennifer, additional, Uckert, Kyle, additional, Malaska, Michael, additional, Patthoff, Alex, additional, Ries, Paul, additional, Budney, Charles, additional, and Mitchell, Karl, additional

Published
2014
Full Text
View/download PDF

23. Comparison of 3D kinetic and hydrodynamic models to ROSINA-COPS measurements of the neutral coma of 67P/Churyumov-Gerasimenko

Author

Bieler, Andre, Altwegg, Kathrin, Balsiger, Hans, Berthelier, Jean-Jacques, Calmonte, Ursina Maria, Combi, Michael, De Keyser, Johan, Fiethe, Björn, Fougere, Nicolas, Fuselier, Stephen, Gasc, Sébastien, Gombosi, Tamas, Hansen, Kenneth, Hässig, Myrtha, Huang, Zhenguang, Jäckel, Annette, Jia, Xianzhe, Le Roy, Lena, Mall, Urs A., Rème, Henri, Rubin, Martin, Tenishev, Valeriy, Tóth, Gábor, Tzou, Chia-Yu, and Wurz, Peter

Subjects
13. Climate action, 520 Astronomy, 620 Engineering
Abstract

67P/Churyumov-Gerasimenko (67P) is a Jupiter-family comet and the object of investigation of the European Space Agency mission Rosetta. This report presents the first full 3D simulation results of 67P’s neutral gas coma. In this study we include results from a direct simulation Monte Carlo method, a hydrodynamic code, and a purely geometric calculation which computes the total illuminated surface area on the nucleus. All models include the triangulated 3D shape model of 67P as well as realistic illumination and shadowing conditions. The basic concept is the assumption that these illumination conditions on the nucleus are the main driver for the gas activity of the comet. As a consequence, the total production rate of 67P varies as a function of solar insolation. The best agreement between the model and the data is achieved when gas fluxes on the night side are in the range of 7% to 10% of the maximum flux, accounting for contributions from the most volatile components. To validate the output of our numerical simulations we compare the results of all three models to in situ gas number density measurements from the ROSINA COPS instrument. We are able to reproduce the overall features of these local neutral number density measurements of ROSINA COPS for the time period between early August 2014 and January 1 2015 with all three models. Some details in the measurements are not reproduced and warrant further investigation and refinement of the models. However, the overall assumption that illumination conditions on the nucleus are at least an important driver of the gas activity is validated by the models. According to our simulation results we find the total production rate of 67P to be constant between August and November 2014 with a value of about 1 × 10²⁶ molecules s⁻¹.

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

Author

Bieler, André, Shou, Y., Fougere, Nicolas, Bockelée-Morvan, D., Combi, M. R., Calmonte, Ursina Maria, Huang, Z., Leyrat, C., Piccioni, G., De Keyser, J., Toth, G., Erard, S., Migliorini, A., Le Roy, L., Filacchione, G., Rubin, Martin, Hansen, K. C., Fink, U., Fuselier, S. A., Tzou, Chia-Yu, Rinaldi, G., Capaccioni, F., Tenishev, V., Hässig, Myrtha, Debout, V., Altwegg, Kathrin, Gombosi, T. I., Berthelier, J.-J., and Fiethe, B.

Subjects
13. Climate action, 530 Physics, 520 Astronomy, 620 Engineering
Abstract

We 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/ChuryumovGerasimenko (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. 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 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.

25. 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

Author

Combi, Michael, Shou, Yinsi, Fougere, Nicolas, Tenishev, Valeriy, Altwegg, Kathrin, Rubin, Martin, Bockelée-Morvan, Dominique, Capaccioni, Fabrizio, Cheng, Yu-Chi, Fink, Uwe, Gombosi, Tamas, Hansen, Kenneth C., Huang, Zhenguang, Marshall, David, and Toth, Gabor

Subjects
13. Climate action, 520 Astronomy, Astrophysics::Earth and Planetary Astrophysics, 620 Engineering, 7. Clean energy
Abstract

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) suite of instruments operated throughout the over two years of the Rosetta mission operations in the vicinity of comet 67P/Churyumov-Gerasimenko. It measured gas densities and composition throughout the comet's atmosphere, or coma. Here we present two-years' worth of measurements of the relative densities of the four major volatile species in the coma of the comet, H₂O, CO₂, CO and O₂, by one of the ROSINA sub-systems called the Double Focusing Mass Spectrometer (DFMS). The absolute total gas densities were provided by the Comet Pressure Sensor (COPS), another ROSINA sub-system. DFMS is a very high mass resolution and high sensitivity mass spectrometer able to resolve at a tiny fraction of an atomic mass unit. We have analyzed the combined DFMS and COPS measurements using an inversion scheme based on spherical harmonics that solves for the distribution of potential surface activity of each species as the comet rotates, changing solar illumination, over short time intervals and as the comet changes distance from the sun and orientation of its spin axis over long time intervals. We also use the surface boundary conditions derived from the inversion scheme to simulate the whole coma with our fully kinetic Direct Simulation Monte Carlo model and calculate the production rates of the four major species throughout the mission. We compare the derived production rates with revised remote sensing observations by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) as well as with published observations from the Microwave Instrument for the Rosetta Orbiter (MIRO). Finally we use the variation of the surface production of the major species to calculate the total mass loss over the mission and, for different estimates of the dust/gas ratio, calculate the variation of surface loss all over the nucleus.

26. Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles

Author

Blum, Jürgen, Gundlach, Bastian, Krause, Maya, Fulle, Marco, Johansen, Anders, Agarwal, Jessica, Borstel, Ingo von, Shi, Xian, Hu, Xuanyu, Bentley, Mark S., Capaccioni, Fabrizio, Colangeli, Luigi, Corte, Vincenzo Della, Fougere, Nicolas, Green, Simon F., Ivanovski, Stavro, Mannel, Thurid, Merouane, Sihane, Migliorini, Alessandra, Rotundi, Alessandra, Schmied, Roland, Snodgrass, Colin, Blum, Jürgen, Gundlach, Bastian, Krause, Maya, Fulle, Marco, Johansen, Anders, Agarwal, Jessica, Borstel, Ingo von, Shi, Xian, Hu, Xuanyu, Bentley, Mark S., Capaccioni, Fabrizio, Colangeli, Luigi, Corte, Vincenzo Della, Fougere, Nicolas, Green, Simon F., Ivanovski, Stavro, Mannel, Thurid, Merouane, Sihane, Migliorini, Alessandra, Rotundi, Alessandra, Schmied, Roland, and Snodgrass, Colin

Abstract

The processes that led to the formation of the planetary bodies in the Solar System are still not fully understood. Using the results obtained with the comprehensive suite of instruments on-board ESA’s Rosetta mission, we present evidence that comet 67P/Churyumov-Gerasimenko likely formed through the gentle gravitational collapse of a bound clump of mm-sized dust aggregates (“pebbles”), intermixed with microscopic ice particles. This formation scenario leads to a cometary make-up that is simultaneously compatible with the global porosity, homogeneity, tensile strength, thermal inertia, vertical temperature profiles, sizes and porosities of emitted dust, and the steep increase in water-vapour production rate with decreasing heliocentric distance, measured by the instruments on-board the Rosetta spacecraft and the Philae lander. Our findings suggest that the pebbles observed to be abundant in protoplanetary discs around young stars provide the building material for comets and other minor bodies.

27. Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles

Author

Blum, Jürgen, Gundlach, Bastian, Krause, Maya, Fulle, Marco, Johansen, Anders, Agarwal, Jessica, Borstel, Ingo von, Shi, Xian, Hu, Xuanyu, Bentley, Mark S., Capaccioni, Fabrizio, Colangeli, Luigi, Corte, Vincenzo Della, Fougere, Nicolas, Green, Simon F., Ivanovski, Stavro, Mannel, Thurid, Merouane, Sihane, Migliorini, Alessandra, Rotundi, Alessandra, Schmied, Roland, Snodgrass, Colin, Blum, Jürgen, Gundlach, Bastian, Krause, Maya, Fulle, Marco, Johansen, Anders, Agarwal, Jessica, Borstel, Ingo von, Shi, Xian, Hu, Xuanyu, Bentley, Mark S., Capaccioni, Fabrizio, Colangeli, Luigi, Corte, Vincenzo Della, Fougere, Nicolas, Green, Simon F., Ivanovski, Stavro, Mannel, Thurid, Merouane, Sihane, Migliorini, Alessandra, Rotundi, Alessandra, Schmied, Roland, and Snodgrass, Colin

Abstract

The processes that led to the formation of the planetary bodies in the Solar System are still not fully understood. Using the results obtained with the comprehensive suite of instruments on-board ESA’s Rosetta mission, we present evidence that comet 67P/Churyumov-Gerasimenko likely formed through the gentle gravitational collapse of a bound clump of mm-sized dust aggregates (“pebbles”), intermixed with microscopic ice particles. This formation scenario leads to a cometary make-up that is simultaneously compatible with the global porosity, homogeneity, tensile strength, thermal inertia, vertical temperature profiles, sizes and porosities of emitted dust, and the steep increase in water-vapour production rate with decreasing heliocentric distance, measured by the instruments on-board the Rosetta spacecraft and the Philae lander. Our findings suggest that the pebbles observed to be abundant in protoplanetary discs around young stars provide the building material for comets and other minor bodies.

29. The Complex Outgassing of Comets and the Resulting Coma, a Direct Simulation Monte-Carlo Approach.

Author

Fougere, Nicolas

Subjects
Comet, Coma, DSMC
Abstract

During its journey, when a comet gets within a few astronomical units of the Sun, solar heating liberates gases and dust from its icy nucleus forming a rarefied cometary atmosphere, the so-called coma. This tenuous atmosphere can expand to distances up to millions of kilometers representing orders of magnitude larger than the nucleus size. Most of the practical cases of coma studies involve the consideration of rarefied gas flows under non-LTE conditions where the hydrodynamics approach is not valid. Then, the use of kinetic methods is required to properly study the physics of the cometary coma. The Direct Simulation Monte-Carlo method is the method of choice to solve the Boltzmann equation, giving the opportunity to study the cometary atmosphere from the inner coma where collisions dominate and is in thermodynamic equilibrium to the outer coma where densities are lower and free flow conditions are verified. While previous studies of the coma used direct sublimation from the nucleus for spherically symmetric 1D models, or 2D models with a day/night asymmetry, recent observations of comets showed the existence of local small source areas such as jets, and extended sources via sublimating icy grains, that must be included into cometary models for a realistic representation of the physics of the coma. In this work, we present, for the first time, 1D, 2D, and 3D models that can take into account the full effects of conditions with more complex sources of gas with jets and/or icy grains. Moreover, an innovative work in a full 3D description of the cometary coma using a kinetic method with a realistic nucleus and outgassing is demonstrated. While most of the physical models used in this study had already been developed, they are included in one self-consistent coma model for the first time. The inclusion of complex cometary outgassing processes represents the state-of-the-art of cometary coma modeling. This provides invaluable information about the coma by refining the understanding of the material that constitutes comets. This helps us to comprehend the process of the Solar System formation, one of the top priority questions in the 2013-2022 Planetary Science Decadal survey.

Published
2014

Catalog

Books, media, physical & digital resources
See catalog results