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An orbital water-ice cycle on comet 67P from colour changes

Filacchione, Gianrico and Capaccioni, Fabrizio and Ciarniello, Mauro and Raponi, Andrea and Rinaldi, Giovanna and De Sanctis, Maria Cristina and Bockelée-Morvan, Dominique and Erard, Stéphane and Arnold, Gabriele and Mennella, Vito and Formisano, Michelangelo and Longobardo, Andrea and Mottola, Stefano (2020) An orbital water-ice cycle on comet 67P from colour changes. Nature, 578 (7793), pp. 49-52. Nature Publishing Group. doi: 10.1038/s41586-020-1960-2. ISSN 0028-0836.

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Official URL: https://www.nature.com/articles/s41586-020-1960-2

Abstract

Solar heating of a cometary surface provides the energy necessary to sustain gaseous activity, through which dust is removed. In this dynamical environment, both the coma and the nucleus evolve during the orbit, changing their physical and compositional properties. The environment around an active nucleus is populated by dust grains with complex and variegated shapes, lifted and diffused by gases freed from the sublimation of surface ices. The visible colour of dust particles is highly variable: carbonaceous organic material-rich grains appear red while magnesium silicate-rich and water-ice-rich grains appear blue, with some dependence on grain size distribution, viewing geometry, activity level and comet family type. We know that local colour changes are associated with grain size variations, such as in the bluer jets made of submicrometre grains on comet Hale-Bopp or in the fragmented grains in the coma of C/1999 S4 (LINEAR). Apart from grain size, composition also influences the coma's colour response, because transparent volatiles can introduce a substantial blueing in scattered light, as observed in the dust particles ejected after the collision of the Deep Impact probe with comet 9P/Tempel 1. Here we report observations of two opposite seasonal colour cycles in the coma and on the surface of comet 67P/Churyumov-Gerasimenko through its perihelion passage. Spectral analysis indicates an enrichment of submicrometre grains made of organic material and amorphous carbon in the coma, causing reddening during the passage. At the same time, the progressive removal of dust from the nucleus causes the exposure of more pristine and bluish icy layers on the surface. Far from the Sun, we find that the abundance of water ice on the nucleus is reduced owing to redeposition of dust and dehydration of the surface layer while the coma becomes less red.

Item URL in elib:https://elib.dlr.de/138639/
Document Type:Article
Title:An orbital water-ice cycle on comet 67P from colour changes
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Filacchione, GianricoINAF-IASF via del Fosso del Cavaliere, 100, 00133 Roma, ItalyUNSPECIFIED
Capaccioni, FabrizioINAF-IAPS, Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, 00133UNSPECIFIED
Ciarniello, MauroIstituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Rome, ItalyUNSPECIFIED
Raponi, AndreaIstituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Rome, ItalyUNSPECIFIED
Rinaldi, GiovannaIstituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Rome, ItalyUNSPECIFIED
De Sanctis, Maria CristinaIstituto di Astrofisica e Planetologia Spaziali, Rom, IUNSPECIFIED
Bockelée-Morvan, DominiqueLESIA, Observatoire de Paris, Université PSL, CNRS, Université de Paris, Sorbonne Université, Meudon, FranceUNSPECIFIED
Erard, StéphaneLESIA, UMR CNRS 8109, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon Cédex, FranceUNSPECIFIED
Arnold, GabrieleGabriele.Arnold (at) dlr.deUNSPECIFIED
Mennella, VitoOsservatorio Astronomico di Capodimonte, Instituto Nazionale di Astrofisica, Naples, ItalyUNSPECIFIED
Formisano, MichelangeloINAF, IAPS, Rome, ItalyUNSPECIFIED
Longobardo, AndreaINAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, 00133 Rome, ItalyUNSPECIFIED
Mottola, Stefanostefano.mottola (at) dlr.dehttps://orcid.org/0000-0002-0457-3872
Date:2020
Journal or Publication Title:Nature
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:578
DOI :10.1038/s41586-020-1960-2
Page Range:pp. 49-52
Publisher:Nature Publishing Group
ISSN:0028-0836
Status:Published
Keywords:comets, 67P/Churyumov-Gerasimenko, sublimation
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project ROSETTA Instruments
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Institute of Planetary Research > Leitungsbereich PF
Institute of Planetary Research > Planetary Geodesy
Deposited By: Mottola, Dr.phys. Stefano
Deposited On:03 Dec 2020 15:02
Last Modified:03 Dec 2020 15:02

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