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The temporal evolution of exposed water ice-rich areas on the surface of 67P/Churyumov-Gerasimenko: spectral analysis

Raponi, A. and Ciarniello, M. and Capaccioni, F. and Filacchione, G. and Tosi, F. and Desanctis, M.C. and Capria, M. T. and Barucci, M. A. and Longobardo, A and Palomba, E. and Kappel, David and Arnold, Gabriele and Mottola, S. and Rousseau, Batiste and Rinaldi, G. and Erard, S. and Bockelee-Morvan, D. and Leyrat, C. (2016) The temporal evolution of exposed water ice-rich areas on the surface of 67P/Churyumov-Gerasimenko: spectral analysis. In: Comets Symposium: A new vision after Rosetta and Philae, p. 114. Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016, 14-18 November 2016, Toulouse.

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Official URL: http://www.comets2016toulouse.com

Abstract

Water ice-rich patches have been detected on the surface of comet 67P/Churyumov-Gerasimenko by the VIRTIS hyperspectral imager on-board the Rosetta spacecraft, since the orbital insertion in late August 2014. Among those, three icy patches have been selected, and VIRTIS data have been used to analyse their properties and temporal evolution while the comet was moving towards the Sun. We performed an extensive analysis of the spectral parameters, and we applied the Hapke radiative transfer model to retrieve the abundance and grain size of water ice, as well as the mixing modalities of water ice and the ubiquitous dark refractory terrains of the surface. Study of the spatial distribution of the spectral parameters within the ice-rich patches has revealed that water ice follows different patterns associated to a bimodal distribution of the grains: ~50 μm sized and ~2000 μm sized, respectively in intimate and areal mixture with the dark material. In all three cases we identified different stages of the evolution of abundance of ice in the selected patches after the first detections at about 3.5 AU heliocentric distance; the spatial extension and intensity of the water ice spectral features reached a maximum after 60-100 days at about 3.0 AU, was followed by an approximately equally timed decrease, and the features were no longer visible when observed again at about ~2.2 AU, before perihelion. The exposure of deeper layers is consistent with their occurrence in “active” areas where falls or landslides could have caused the occasional exposure of water ice-rich layers. After the initial exposure of the ice, the activity of the affected area increases thus causing dust removal powered by sublimation, which provides a positive feedback on the exposure itself. The process develops as the solar flux increases, and it reaches a turning point when the exposure rate is outweighed by the sublimation rate, until the complete sublimation of the patch. It is interesting to note that the behaviour of the analysed patches was very similar with a lifecycle of about 180 days, which can be ascribed to a seasonal cycle. In addition to the observed seasonal cycle we found evidence of short-term variability associated to a diurnal water cycle. Our analysis, in addition to previous work (Filacchione et al., 2016; Barucci et al., 2016; Ciarniello et al., 2016), indicates that water ice is rather evenly distributed in the subsurface and that no large water ice reservoirs are present.

Item URL in elib:https://elib.dlr.de/115313/
Document Type:Conference or Workshop Item (Poster)
Title:The temporal evolution of exposed water ice-rich areas on the surface of 67P/Churyumov-Gerasimenko: spectral analysis
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Raponi, A.inaf-iasf, italyUNSPECIFIED
Ciarniello, M.inaf-iasf, italyUNSPECIFIED
Capaccioni, F.inaf-iasf, italyUNSPECIFIED
Filacchione, G.inaf-iasf, rome, italyUNSPECIFIED
Tosi, F.inaf-iasf istituto di astrofisica spaziale e fisica cosmica, roma italyUNSPECIFIED
Desanctis, M.C.inaf, istituto di astrofisica spaziale e fisica cosmica, roma, italyUNSPECIFIED
Capria, M. T.instituto di astrofisica spaziale e fisica cosmica, roma, italyUNSPECIFIED
Barucci, M. A.observatoire de paris, meudon, franceUNSPECIFIED
Longobardo, Ainaf-laps, via del fosso del cavaliere 100, i-00133 rome, italyUNSPECIFIED
Palomba, E.institute for interplanetary space physics - inaf, rome, italyUNSPECIFIED
Kappel, Daviddavid.kappel (at) dlr.deUNSPECIFIED
Arnold, Gabrielegabriele.arnold (at) dlr.deUNSPECIFIED
Mottola, S.stefano.mottola (at) dlr.deUNSPECIFIED
Rousseau, BatistelesiaUNSPECIFIED
Rinaldi, G.istituto di fisica dello spazio interplanetario (ifsi-inaf), rome - italyUNSPECIFIED
Erard, S.lesiaUNSPECIFIED
Bockelee-Morvan, D.observatoire de paris, meudonUNSPECIFIED
Leyrat, C.lesiaUNSPECIFIED
Date:November 2016
Journal or Publication Title:Comets Symposium: A new vision after Rosetta and Philae
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Page Range:p. 114
Status:Published
Keywords:VIRTIS, comets, spectrophotometry, Rosetta, 67P, water ice
Event Title:Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016
Event Location:Toulouse
Event Type:international Conference
Event Dates:14-18 November 2016
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt ROSETTA Instrumente
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Institute of Planetary Research > Leitungsbereich PF
Deposited By: Kappel, David
Deposited On:20 Nov 2017 15:03
Last Modified:20 Nov 2017 15:03

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