The Agilkia boulders/pebbles size–frequency distributions: OSIRIS and ROLIS joint observations of 67P surface Free

Pajola, M.; Mottola, S.; Hamm, M.; Fulle, M.; Davidsson, B.; Güttler, C.; Sierks, H.; Naletto, G.; Arnold, G.; Grothues, H.-G.; Jaumann, R.; Michaelis, H.; Bibring, J. P.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A’Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Feller, C.; Fornasier, S.; Gicquel, A.; Groussin, O.; Gutierrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lin, Z. Y.; Lazzarin, M.; Lopez Moreno, J. J.; Lucchetti, A.; Marzari, F.; Massironi, M.; Michalik, H.; Oklay, N.; Pommerol, A.; Preusker, F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J. B.

Research article (journal) | Peer reviewed

Abstract

By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size–frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05–30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders ‘peek through’ the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.

Details about the publication

JournalMonthly Notices of the Royal Astronomical Society
Volume462
Issue1
Page range242-252
StatusPublished
Release year2016 (23/10/2016)
Language in which the publication is writtenEnglish
DOI10.1093/mnras/stw2720
Link to the full texthttps://academic.oup.com/mnras/article/462/Suppl_1/S242/2417444
Keywordsmethods: data analysis; methods: statistical; comets: individual: 67P C-G

Authors from the University of Münster

Arnold, Gabriele
Institute for Planetology
Güttler, Carsten
Professorship of experimental and analytical planetology (Prof. Gundlach)