TY  - JOUR
A1  - Rousseau, Batiste
A1  - Erard, Stéphane
A1  - Beck, P.
A1  - Quirico, Eric
A1  - Schmitt, B.
A1  - Brissaud, O.
A1  - Montes-Hernandez, G.
A1  - Capaccioni, F.
A1  - Filacchione, Gianrico
A1  - Bockelee-Morvan, Dominique
A1  - Leyrat, C.
A1  - Ciarniello, M.
A1  - Raponi, Andrea
A1  - Kappel, David
A1  - Arnold, G.
A1  - Moroz, L. V.
A1  - Palomba, Ernesto
A1  - Tosi, Federico
T1  - Laboratory simulations of the Vis-NIR spectra of comet 67P using sub-mu m sized cosmochemical analogues
JF  - Icarus : international journal of solar system studies
N2  - Laboratory spectral measurements of relevant analogue materials were performed in the framework of the Rosetta mission in order to explain the surface spectral properties of comet 67P. Fine powders of coal, iron sulphides, silicates and their mixtures were prepared and their spectra measured in the Vis-IR range. These spectra are compared to a reference spectrum of 67P nucleus obtained with the VIRTIS/Rosetta instrument up to 2.7 mu m, excluding the organics band centred at 3.2 mu m. The species used are known to be chemical analogues for cometary materials which could be present at the surface of 67P. Grain sizes of the powders range from tens of nanometres to hundreds of micrometres. Some of the mixtures studied here actually reach the very low reflectance level observed by VIRTIS on 67P. The best match is provided by a mixture of sub-micron coal, pyrrhotite, and silicates. Grain sizes are in agreement with the sizes of the dust particles detected by the GIADA, MIDAS and COSIMA instruments on board Rosetta. The coal used in the experiment is responsible for the spectral slope in the visible and infrared ranges. Pyrrhotite, which is strongly absorbing, is responsible for the low albedo observed in the NIR. The darkest components dominate the spectra, especially within intimate mixtures. Depending on sample preparation, pyrrhotite can coat the coal and silicate aggregates. Such coating effects can affect the spectra as much as particle size. In contrast, silicates seem to play a minor role. (c) 2017 Elsevier Inc. All rights reserved.
KW  - Comets
KW  - Comets nucleus
KW  - Comets composition
KW  - Spectroscopy
KW  - Experimental techniques
Y1  - 2018
U6  - https://doi.org/10.1016/j.icarus.2017.10.015
SN  - 0019-1035
SN  - 1090-2643
VL  - 306
SP  - 306
EP  - 318
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Tosi, Federico
A1  - Capaccioni, F.
A1  - Capria, M. T.
A1  - Mottola, Stefano
A1  - Zinzi, A.
A1  - Ciarniello, M.
A1  - Filacchione, G.
A1  - Hofstadter, M.
A1  - Fonti, S.
A1  - Formisano, M.
A1  - Kappel, David
A1  - Kührt, E.
A1  - Leyrat, C.
A1  - Vincent, J-B
A1  - Arnold, G.
A1  - De Sanctis, M. C.
A1  - Longobardo, Andrea
A1  - Palomba, E.
A1  - Raponi, A.
A1  - Rousseau, Batiste
A1  - Schmitt, Bernard
A1  - Barucci, Maria Antonietta
A1  - Bellucci, Giancarlo
A1  - Benkhoff, Johannes
A1  - Bockelee-Morvan, D.
A1  - Cerroni, P.
A1  - Combe, J-Ph
A1  - Despan, D.
A1  - Erard, Stéphane
A1  - Mancarella, F.
A1  - McCord, T. B.
A1  - Migliorini, Alessandra
A1  - Orofino, V
A1  - Piccioni, G.
T1  - The changing temperature of the nucleus of comet 67P induced by morphological and seasonal effects
JF  - Nature astronomy
N2  - Knowledge of the surface temperature distribution on a comet’s nucleus and its temporal evolution at different timescales is key to constraining its thermophysical properties and understanding the physical processes that take place at and below the surface. Here we report on time-resolved maps of comet 67P/Churyumov–Gerasimenko retrieved on the basis of infrared data acquired by the Visible InfraRed and Thermal Imaging Spectrometer (VIRTIS) onboard the Rosetta orbiter in 2014, over a roughly two-month period in the pre-perihelion phase at heliocentric distances between 3.62 and 3.31 au from the Sun. We find that at a spatial resolution ≤15 m per pixel, the measured temperatures point out the major effect that self-heating, due to the complex shape of the nucleus, has on the diurnal temperature variation. The bilobate nucleus of comet 67P also induces daytime shadowing effects, which result in large thermal gradients. Over longer periods, VIRTIS-derived temperature values reveal seasonal changes driven by decreasing heliocentric distance combined with an increasing abundance of ice within the uppermost centimetre-thick layer, which implies the possibility of having a largely pristine nucleus interior already in the shallow subsurface
Y1  - 2019
U6  - https://doi.org/10.1038/s41550-019-0740-0
SN  - 2397-3366
VL  - 3
IS  - 7
SP  - 649
EP  - 658
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Ciarniello, Mauro
A1  - Fulle, Marco
A1  - Raponi, Andrea
A1  - Filacchione, Gianrico
A1  - Capaccioni, Fabrizio
A1  - Rotundi, Alessandra
A1  - Rinaldi, Giovanna
A1  - Formisano, Michelangelo
A1  - Magni, Gianfranco
A1  - Tosi, Federico
A1  - De Sanctis, Maria Cristina
A1  - Capria, Maria Teresa
A1  - Longobardo, Andrea
A1  - Beck, Pierre
A1  - Fornasier, Sonia
A1  - Kappel, David
A1  - Mennella, Vito
A1  - Mottola, Stefano
A1  - Rousseau, Batiste
A1  - Arnold, Gabriele
T1  - Macro and micro structures of pebble-made cometary nuclei reconciled by seasonal evolution
JF  - Nature astronomy
N2  - Comets evolve due to sublimation of ices embedded inside porous dust, triggering dust emission (that is, erosion) followed by mass loss, mass redistribution and surface modifications. Surface changes were revealed by the Deep Impact and Stardust NExT missions for comet 9P/Tempel 1 (ref.(1)), and a full inventory of the processes modifying cometary nuclei was provided by Rosetta while it escorted comet 67P/Churyumov-Gerasimenko for approximately two years(2-4). Such observations also showed puzzling water-ice-rich spots that stood out as patches optically brighter and spectrally bluer than the average cometary surfaces(5-9). These are up to tens of metres large and indicate macroscopic compositional dishomogeneities apparently in contrast with the structural homogeneity above centimetre scales of pebble-made nuclei(10). Here we show that the occurrence of blue patches determines the seasonal variability of the nucleus colour(4,11,12) and gives insight into the internal structure of comets. We define a new model that links the centimetre-sized pebbles composing the nucleus(10) and driving cometary activity(13,14) to metre-sized water-ice-enriched blocks embedded in a drier matrix. The emergence of blue patches is due to the matrix erosion driven by CO2-ice sublimation that exposes the water-ice-enriched blocks, which in turn are eroded by water-ice sublimation when exposed to sunlight. Our model explains the observed seasonal evolution of the nucleus and reconciles the available data at micro (sub-centimetre) and macro (metre) scales.
KW  - Asteroids, comets and Kuiper belt
KW  - Planetary science
Y1  - 2022
U6  - https://doi.org/10.1038/s41550-022-01625-y
SN  - 2397-3366
VL  - 6
IS  - 5
SP  - 546
EP  - 553
PB  - Nature Research
CY  - Berlin
ER  -