Volume 591, July 2016
|Number of page(s)||17|
|Section||Planets and planetary systems|
|Published online||07 June 2016|
Electrical properties and porosity of the first meter of the nucleus of 67P/Churyumov-Gerasimenko
As constrained by the Permittivity Probe SESAME-PP/Philae/Rosetta
LATMOS/IPSL, UVSQ Universités Paris-Saclay, UPMC Univ. Paris 06,
2 LATMOS/IPSL, UPMC Univ. Paris 06 Sorbonne Universités, UVSQ, CNRS, 75005 Paris, France
3 Finnish Meteorological Institute, 00560 Helsinki, Finland
4 Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Rutherfordstraße 2, 12489 Berlin, Germany
5 Retired from ESA/ESTEC, 11 rue des Forges, Paunay, 79400 Saivres, France
6 Deutsches Zentrum für Luft- und Raumfahrt, Raumflugbetrieb und Astronautentraining, MUSC, Linder Höhe, 51147 Köln, Germany
7 ESA/ESTEC, 2201 AZ Noordwijk, The Netherlands
Received: 12 February 2016
Accepted: 23 March 2016
Context. Comets are primitive objects, remnants of the volatile-rich planetesimals from which the solar system condensed. Knowing their structure and composition is thus crucial for the understanding of our origins. After the successful landing of Philae on the nucleus of 67P/Churyumov-Gerasimenko in November 2014, for the first time, the Rosetta mission provided the opportunity to measure the low frequency electrical properties of a cometary mantle with the permittivity probe SESAME-PP (Surface Electric Sounding and Acoustic Monitoring Experiment−Permittivity Probe).
Aims. In this paper, we conduct an in-depth analysis of the data from active measurements collected by SESAME-PP at Abydos, which is the final landing site of Philae, to constrain the porosity and, to a lesser extent, the composition of the surface material down to a depth of about 1 m.
Methods. SESAME-PP observations on the surface are then analyzed by comparison with data acquired during the descent toward the nucleus and with numerical simulations that explore different possible attitudes and environments of Philae at Abydos using a method called the Capacity-Influence Matrix Method.
Results. Reasonably assuming that the two receiving electrode channels have not drifted with respect to each other during the ten-year journey of the Rosetta probe to the comet, we constrain the dielectric constant of the first meter below the surface at Abydos to be >2.45 ± 0.20, which is consistent with a porosity <50% if the dust phase is analogous to carbonaceous chondrites and <75% in the case of less primitive ordinary chondrites. This indicates that the near surface of the nucleus of 67P/Churyumov-Gerasimenko is more compacted than its interior and suggests that it could consist of a sintered dust-ice layer.
Key words: comets: individual: 67P/Churyumov-Gerasimenko / methods: numerical / methods: data analysis / space vehicles: instruments / planets and satellites: surfaces
© ESO, 2016
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