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Remote Boulder counting and thermal IR temperature curves constrain strength, microporosity, thermal conductivity and grain density of rubble pile Ryugu's rock

Biele, Jens and Grott, Matthias and Hamm, Maximilian and Michel, Patrick and Sugita, Seiji and Sakatani, Naoya and Neumann, Wladimir and Kameda, Shingo and Michikami, Tatsuhiro and Honda, Chikatoshi (2021) Remote Boulder counting and thermal IR temperature curves constrain strength, microporosity, thermal conductivity and grain density of rubble pile Ryugu's rock. SOFIA Rock, Dust and Ice Interpreting Planetary Data Virtual Workshop, 23. - 26. März 2021, Virtuell.

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Abstract

In this paper, we summarize the findings and deductions for small asteroid Ryugu from Hayabusa2 remote sensing as well as from MASCOT radiometer (MARA) data. Observations cover the VIS (broadband) and MIR (broadband) wavelength ranges. For a typical rock on Ryugu's surface, we find a thermal inertia of 295±18 Jm-2K-1s-1/2 (Hamm+ 2020), a microporosity of 50 ± 3% (Grott+ 2020, Hamm+, 2020), and assuming a CM composition and thus an inferred specific heat capacity of cp = 890 Jkg-1K-1 (± 10%, at an average temperature of 277 K), we estimate a thermal conductivity of 0.069 ± 0.012 Jm-1K-1 at ~277 K. These estimates are based on MARA surface brightness temperature measurements of an arguably (Biele+ 2019) dust-free boulder at MASCOT's landing site obtained over a full diurnal cycle. Those values are consistent with the TIR instrument's global findings (Okada+ 2020). The main source of uncertainty in the thermal inertia estimate is due to the uncertain surface orientation of the boulder top that determines the insolation power. Including a Digital Terrain Model (DTM) of the observed boulder, embedded in the MASCOT landing site (Scholten+, 2019), into the thermal model could reduce this uncertainty significantly. The very high deduced microporosity lets us reasonably estimate the tensile strength of those abundant "cauliflower rocks" (Jaumann+, 2019), ~200-280 kPa (Grott+, 2019).

Item URL in elib:https://elib.dlr.de/142592/
Document Type:Conference or Workshop Item (Speech)
Title:Remote Boulder counting and thermal IR temperature curves constrain strength, microporosity, thermal conductivity and grain density of rubble pile Ryugu's rock
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Biele, JensJens.Biele (at) dlr.deUNSPECIFIED
Grott, MatthiasMatthias.Grott (at) dlr.deUNSPECIFIED
Hamm, Maximilianmaximilian.hamm (at) dlr.deUNSPECIFIED
Michel, PatrickObservatoire de la Côte d'Azur, NiceUNSPECIFIED
Sugita, SeijiUniversity of Tokyo, Tokyo, JapanUNSPECIFIED
Sakatani, NaoyaRikkyo University JapanUNSPECIFIED
Neumann, WladimirWladimir.Neumann (at) dlr.deUNSPECIFIED
Kameda, ShingoRikkyo University, JapanUNSPECIFIED
Michikami, TatsuhiroKindai University, Hiroshima, JapanUNSPECIFIED
Honda, ChikatoshiUniv Aizu, Res Ctr Adv Informat Sci & Technol, Aizu Wakamatsu, Fukushima, JapanUNSPECIFIED
Date:23 March 2021
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Ryugu, IR temperature, microporosity
Event Title:SOFIA Rock, Dust and Ice Interpreting Planetary Data Virtual Workshop
Event Location:Virtuell
Event Type:Workshop
Event Dates:23. - 26. März 2021
Organizer:Sofia Science Center
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project MASCOT - Science
Location: Berlin-Adlershof , Köln-Porz
Institutes and Institutions:Space Operations and Astronaut Training > User center for space experiments (MUSC)
Institute of Planetary Research > Planetary Physics
Deposited By: Herrmann, Astrid
Deposited On:03 Jun 2021 07:00
Last Modified:03 Jun 2021 07:00

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