Rosetta/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry

Feller, C.; Fornasier, S.; Ferrari, Sabrina; Hasselmann, P. H.; Barucci, A.; Massironi, Matteo; Deshapriya, J. D. P.; Sierks, H.; Naletto, G.; Lamy, Philippe; Rodrigo, R.; Koschny, D.; Davidsson, B.; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits, Dennis; Cremonese, G.; Deppo, V. Da; Debei, S.; Cecco, M. De; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W.-H.; Keller, H. U.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Shi, Xian; Tubiana, C.; Gaskell, B.; Forgia, Fiorangela La; Lucchetti, Alice; Mottola, S.; Pajola, M.; Preusker, Frank; Scholten, F.

doi:10.1051/0004-6361/201833807

Cited by 8 publications

(2 citation statements)

References 64 publications

(102 reference statements)

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“…A special spectral behavior for ROI 5 was also noted by Feller et al (2019). ROI 5 corresponds to the Cuesta feature that was analyzed by these authors.…”

Section: Phase-ratio Analysismentioning

confidence: 62%

Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Masoumzadeh

Kolokolova

Tubiana

et al. 2019

A&A

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Aims. The Rosetta-OSIRIS images acquired at small phase angles in three wavelengths during the fly-by of the spacecraft on 9-10 April 2016 provided a unique opportunity to study the opposition effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our goal is to study phase curves of the nucleus at small phase angles for a variety of surface structures to show the differences in their opposition effect and to determine which surface properties cause the differences. Methods. We used OSIRIS NAC images that cover the Ash-Khepry-Imhotep region to extract the phase curve, that is, the reflectance of the surface as a function of phase angle. We selected six regions of interest (ROIs) and derived the phase curves for each ROI. We fit a linear-exponential function to the phase curves. The resulting model parameters were then interpreted by spectrophotometric, geomorphological, and phase-ratio analyses, and by investigating the influence of structural and textural properties of the surface. Results. We find evidence for the opposition effect (deviation of the phase curve from linear behavior) in phase curves for all areas. We found an anticorrelation between the phase ratio and reflectance in a small phase angle range. This provides evidence for the shadowhiding effect. We conclude that the decrease in the slope of the phase ratio versus reflectance indicates a decrease in the proportion of shadowed regions and reduces the contribution of the shadow-hiding effect. Large uncertainties in the determination of the opposition effect parameters with respect to wavelength do not allow us to conclusively claim coherent backscattering in the opposition effect phenomenon. Based on the two analyses, we conclude that the opposition effect of comet 67P in the Ash-Khepry-Imhotep region is mainly affected by shadow-hiding.

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“…A special spectral behavior for ROI 5 was also noted by Feller et al (2019). ROI 5 corresponds to the Cuesta feature that was analyzed by these authors.…”

Section: Phase-ratio Analysismentioning

confidence: 62%

Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Masoumzadeh

Kolokolova

Tubiana

et al. 2019

A&A

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“…Compared to the nucleus of 67P/C-G, these computed spectral slopes are lower than the average terrain of the comet. In the highspatial observations of the nucleus near opposition (Feller et al 2016(Feller et al , 2019, the spectral slope of the typical boulder-less terrain was close to 18 %/100 nm, i.e. about 2.6 times greater than the spectral slope of the 90 % charcoal mixture.…”

Section: Cophylab Dust Spectral Propertiesmentioning

confidence: 88%

Cometary dust analogues for physics experiments

Lethuillier

Feller

Kaufmann

et al. 2022

Monthly Notices of the Royal Astronomical Society

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The CoPhyLab (Cometary Physics Laboratory) project is designed to study the physics of comets through a series of earth-based experiments. For these experiments, a dust analogue was created with physical properties comparable to those of the non-volatile dust found on comets. This ‘CoPhyLab dust’ is planned to be mixed with water and CO2 ice and placed under cometary conditions in vacuum chambers to study the physical processes taking place on the nuclei of comets. In order to develop this dust analogue, we mixed two components representative for the non-volatile materials present in cometary nuclei. We chose silica dust as representative for the mineral phase and charcoal for the organic phase, which also acts as a darkening agent. In this paper, we provide an overview of known cometary analogues before presenting measurements of eight physical properties of different mixtures of the two materials and a comparison of these measurements with known cometary values. The physical properties of interest are: particle size, density, gas permeability, spectrophotometry, mechanical, thermal and electrical properties. We found that the analogue dust that matches the highest number of physical properties of cometary materials consists of a mixture of either 60 per cent/40 per cent or 70 per cent/30 per cent of silica dust/charcoal by mass. These best-fit dust analogue will be used in future CoPhyLab experiments.

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Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko

Fornasier

Hoang

Hasselmann

et al. 2019

A&A

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Aims. The Rosetta space probe accompanied comet 67P/Churyumov-Gerasimenko for more than two years, obtaining an unprecedented amount of unique data of the comet nucleus and inner coma. This has enabled us to study its activity almost continuously from 4 au inbound to 3.6 au outbound, including the perihelion passage at 1.24 au. This work focuses identifying the source regions of faint jets and outbursts and on studying the spectrophotometric properties of some outbursts. We use observations acquired with the OSIRIS/NAC camera during July-October 2015, that is, close to perihelion. Methods. We analyzed more than 2000 images from NAC color sequences acquired with 7-11 filters covering the 250-1000 nm wavelength range. The OSIRIS images were processed with the OSIRIS standard pipeline up to level 3, that is, converted in radiance factor, then corrected for the illumination conditions. For each color sequence, color cubes were produced by stacking registered and illumination-corrected images. Results. More than 200 jets of different intensities were identified directly on the nucleus. Some of the more intense outbursts appear spectrally bluer than the comet dark terrain in the vivible-to-near-infrared region. We attribute this spectral behavior to icy grains mixed with the ejected dust. Some of the jets have an extremely short lifetime. They appear on the cometary surface during the color sequence observations, and vanish in less than some few minutes after reaching their peak. We also report a resolved dust plume observed in May 2016 at a resolution of 55 cm/pixel, which allowed us to estimate an optical depth of ∼0.65 and an ejected mass of ∼ 2200 kg, assuming a grain bulk density of ∼ 800 kg/m 3 . We present the results on the location, duration, and colors of active sources on the nucleus of 67P from the medium-resolution (i.e., 6-10 m/pixel) images acquired close to perihelion passage. The observed jets are mainly located close to boundaries between different morphological regions. Some of these active areas were observed and investigated at higher resolution (up to a few decimeter per pixel) during the last months of operations of the Rosetta mission. Conclusions. These observations allow us to investigate the link between morphology, composition, and activity of cometary nuclei. Jets depart not only from cliffs, but also from smooth and dust-covered areas, from fractures, pits, or cavities that cast shadows and favor the recondensation of volatiles. This study shows that faint jets or outbursts continuously contribute to the cometary activity close to perihelion passage, and that these events are triggered by illumination conditions. Faint jets or outbursts are not associated with a particular terrain type or morphology.Article number, page 22 of 27 S. Fornasier et al.: Jets and activity on comet 67P

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Rosetta/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry

Cited by 8 publications

References 64 publications

Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles

Cometary dust analogues for physics experiments

Linking surface morphology, composition, and activity on the nucleus of 67P/Churyumov-Gerasimenko

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