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Naji, M. |
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Motta, Antonella |
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Aletan, Dirar |
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Mohamed, Tarek |
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Ertürk, Emre |
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Taccardi, Nicola |
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Kononenko, Denys |
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Petrov, R. H. | Madrid |
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Alshaaer, Mazen | Brussels |
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Bih, L. |
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Casati, R. |
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Muller, Hermance |
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Kočí, Jan | Prague |
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Šuljagić, Marija |
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Kalteremidou, Kalliopi-Artemi | Brussels |
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Azam, Siraj |
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Ospanova, Alyiya |
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Blanpain, Bart |
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Ali, M. A. |
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Popa, V. |
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Rančić, M. |
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Ollier, Nadège |
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Azevedo, Nuno Monteiro |
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Landes, Michael |
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Rignanese, Gian-Marco |
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Ciarletti, V.
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Topics
Publications (5/5 displayed)
- 2019The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosettacitations
- 2019WISDOM Calibration Methodology and Instrument Transfer Function Impact on Surface Permittivity Measurements and Depth Resolution
- 2017Subsurface characterization by the ground penetrating radar WISDOM/ExoMars 2020
- 2016A porosity gradient in 67P/C-G nucleus suggested from CONSERT and SESAME-PP results: an interpretation based on new laboratory permittivity measurements of porous icy analoguescitations
- 2011Dielectric and Hardness Measurements of Martian Analog Rocks in Support of the WISDOM Radar on ExoMars
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article
A porosity gradient in 67P/C-G nucleus suggested from CONSERT and SESAME-PP results: an interpretation based on new laboratory permittivity measurements of porous icy analogues
Abstract
The Rosetta spacecraft made a rendezvous with comet 67P/Churyumov-Gerasimenko (67P) in 2014 August, soon after the Philae module landed on the small lobe of the nucleus on 2014 November 12. The CONSERT instrument, onboard Rosetta and Philae, sounded the upper part of the interior of 67P with radiowaves at 90 MHz and determined an average of the real part of the permittivity (hereafter ɛ<SUP>΄</SUP>) equal to about 1.27. The SESAME-PP instrument, onboard Philae, sounded the near-surface of the small lobe in the 400-800 Hz range and determined a lower limit of ɛ<SUP>΄</SUP> equal to 2.45. We use a semi-empirical formula obtained from measurements of ɛ<SUP>΄</SUP> performed in the laboratory at 243 K on water ice and ice-basaltic dust mixtures, with a controlled porosity in the 31-91 per cent range and a dust-to-ice volumetric ratio in the 0.1-2.8 range, to interpret the results of the two instruments, taking into account the temperature and frequency dependences. A graphical method is proposed to derive ranges of porosity and dust-mass fraction from a value of ɛ<SUP>΄</SUP> derived from observations. The non-dispersive behaviour of ɛ<SUP>΄</SUP> below 175 K, allows us to compare the values of ɛ<SUP>΄</SUP> obtained by CONSERT and SESAME-PP. We show that the porosity of the small lobe of 67P increases with depth. Based on new measurements of analogues of complex extraterrestrial organic matter, the so-called tholins, we also suggest that, for the dust component in the cometary material, the presence of silicates has more effect on ɛ<SUP>΄</SUP> than organic materials....