@article{RousseauErardBecketal.2018,
  author    = {Rousseau, Batiste and Erard, St{\´e}phane and Beck, P. and Quirico, Eric and Schmitt, B. and Brissaud, O. and Montes-Hernandez, G. and Capaccioni, F. and Filacchione, Gianrico and Bockelee-Morvan, Dominique and Leyrat, C. and Ciarniello, M. and Raponi, Andrea and Kappel, David and Arnold, G. and Moroz, L. V. and Palomba, Ernesto and Tosi, Federico},
  title     = {Laboratory simulations of the Vis-NIR spectra of comet 67P using sub-mu m sized cosmochemical analogues},
  series = {Icarus : international journal of solar system studies},
  volume    = {306},
  journal   = {Icarus : international journal of solar system studies},
  publisher = {Elsevier},
  address   = {San Diego},
  organization    = {VIRTIS Team},
  issn      = {0019-1035},
  doi       = {10.1016/j.icarus.2017.10.015},
  pages     = {306 -- 318},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{TosiCapaccioniCapriaetal.2019,
  author    = {Tosi, Federico and Capaccioni, F. and Capria, M. T. and Mottola, Stefano and Zinzi, A. and Ciarniello, M. and Filacchione, G. and Hofstadter, M. and Fonti, S. and Formisano, M. and Kappel, David and K{\"u}hrt, E. and Leyrat, C. and Vincent, J-B and Arnold, G. and De Sanctis, M. C. and Longobardo, Andrea and Palomba, E. and Raponi, A. and Rousseau, Batiste and Schmitt, Bernard and Barucci, Maria Antonietta and Bellucci, Giancarlo and Benkhoff, Johannes and Bockelee-Morvan, D. and Cerroni, P. and Combe, J-Ph and Despan, D. and Erard, St{\´e}phane and Mancarella, F. and McCord, T. B. and Migliorini, Alessandra and Orofino, V and Piccioni, G.},
  title     = {The changing temperature of the nucleus of comet 67P induced by morphological and seasonal effects},
  series = {Nature astronomy},
  volume    = {3},
  journal   = {Nature astronomy},
  number    = {7},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2397-3366},
  doi       = {10.1038/s41550-019-0740-0},
  pages     = {649 -- 658},
  year      = {2019},
  abstract  = {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},
  language  = {en}
}