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Appears in Collections:Biological and Environmental Sciences Journal Articles
Peer Review Status: Refereed
Title: Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu
Author(s): Grott, Matthias
Knollenberg, Joerg
Hamm, Maximilian
Ogawa, Kazunori
Jaumann, Ralf
Otto, Katharina
Delbo, Marco
Michel, Patrick
Biele, Jens
Neumann, Wladimir
Knapmeyer, Martin
Kührt, Ekkehard
Senshu, Hiroki
Okada, Tatsuaki
Hagermann, Axel
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Keywords: Asteroids, comets and Kuiper belt
Planetary science
Issue Date: Dec-2019
Citation: Grott M, Knollenberg J, Hamm M, Ogawa K, Jaumann R, Otto K, Delbo M, Michel P, Biele J, Neumann W, Knapmeyer M, Kührt E, Senshu H, Okada T & Hagermann A (2019) Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu. Nature Astronomy, 3, pp. 971-976.
Abstract: C-type asteroids are among the most pristine objects in the Solar System, but little is known about their interior structure and surface properties. Telescopic thermal infrared observations have so far been interpreted in terms of a regolith-covered surface with low thermal conductivity and particle sizes in the centimetre range. This includes observations of C-type asteroid (162173) Ryugu. However, on arrival of the Hayabusa2 spacecraft at Ryugu, a regolith cover of sand- to pebble-sized particles was found to be absent. Rather, the surface is largely covered by cobbles and boulders, seemingly incompatible with the remote-sensing infrared observations. Here we report on in situ thermal infrared observations of a boulder on the C-type asteroid Ryugu. We found that the boulder’s thermal inertia was much lower than anticipated based on laboratory measurements of meteorites, and that a surface covered by such low-conductivity boulders would be consistent with remote-sensing observations. Our results furthermore indicate high boulder porosities as well as a low tensile strength in the few hundred kilopascal range. The predicted low tensile strength confirms the suspected observational bias in our meteorite collections, as such asteroidal material would be too frail to survive atmospheric entry.
DOI Link: 10.1038/s41550-019-0832-x
Rights: This item has been embargoed for a period. During the embargo please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study. Articles published within the Springer Nature group of companies which are made available through academic repositories remain subject to copyright. Grott, M., Knollenberg, J., Hamm, M. et al. Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu. Nat Astron 3, 971–976 (2019) doi:10.1038/s41550-019-0832-x
Notes: Additional co-authors: J Helbert, A Maturilli, N Müller, N Sakatani, S Tanaka, T Arai, S Mottola, S Tachibana, I Pelivan, L Drube, J-B Vincent, H Yano, C Pilorget, K D Matz, N Schmitz, A Koncz, S Schröder, F Trauthan, M Schlotterer, C Krause, T-M Ho and A Moussi-Soffys
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