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Microporosity and parent body of the rubble-pile NEA (162173) Ryugu

Neumann, Wladimir and Grott, Matthias and Trieloff, M. and Jaumann, Ralf and Biele, Jens and Hamm, Maximilian and Kührt, Ekkehard (2020) Microporosity and parent body of the rubble-pile NEA (162173) Ryugu. Icarus. Elsevier. doi: 10.1016/j.icarus.2020.114166. ISSN 0019-1035.

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S0019103520305054

Abstract

Both observations of C-type near-Earth asteroids and laboratory investigations of carbonaceous chondritic meteorites provide strong evidence for a high microporosity of C-type asteroids. Boulder microporosity values derived from in-situ measurements at the surface of the rubble-pile NEA (162173) Ryugu are as high as 55 %, which is substantially higher than for water-rich carbonaceous chondrite samples and could indicate distinct evolution paths for the parent body of Ryugu and parent bodies of carbonaceous chondrites, despite spectral similarities. In the present study, we calculate the evolution of the temperature and porosity for early solar system's planetesimals in order to constrain the range of parameters that result in microporosities compatible with Ryugu's high-porosity material and likely burial depths for the boulders observed at the surface. By varying key properties of the parent body, such as accretion time t0 and radius R that have strong influence on temperature and porosity and by comparing the interior porosity distribution with the measured boulder microporosity, hydration, and partial dehydration of the material, we constrain a field within the (R, t0)-diagram appropriate for bodies that are likely to have produced such material. Our calculations indicate a parent body size of only a few km and its early accretion within ≲2 − 3 Myr after the formation of Ca-Al-rich inclusions (CAIs). A gradual final porosity profile of best-fit bodies indicates production of both low- and high-density boulders from the parent body material. By contrast, parent body properties for CI and CM chondrites obtained by fitting carbonate formation data indicate a radius of ≈20 − 25 km and an accretion time of ≈3.75 Myr after CAIs. These results imply a population of km-sized early accreting highly porous planetesimals as parent bodies of the rubble-pile NEA Ryugu (and, potentially, other NEAs) and a population of larger and late accreting less porous planetesimals as parent bodies of water-rich carbonaceous chondrites.

Item URL in elib:https://elib.dlr.de/139027/
Document Type:Article
Additional Information:Bisher nur online erschienen.
Title:Microporosity and parent body of the rubble-pile NEA (162173) Ryugu
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Neumann, WladimirWladimir.Neumann (at) dlr.deUNSPECIFIED
Grott, MatthiasMatthias.Grott (at) dlr.deUNSPECIFIED
Trieloff, M.Klaus-Tschira-Labor für Kosmochemie, Institut für Geowissenschaften, Universität HeidelbergUNSPECIFIED
Jaumann, RalfFreie Universität Berlinhttps://orcid.org/0000-0002-9759-6597
Biele, JensJens.Biele (at) dlr.deUNSPECIFIED
Hamm, Maximilianmaximilian.hamm (at) dlr.deUNSPECIFIED
Kührt, EkkehardEkkehard.Kuehrt (at) dlr.deUNSPECIFIED
Date:24 October 2020
Journal or Publication Title:Icarus
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1016/j.icarus.2020.114166
Publisher:Elsevier
ISSN:0019-1035
Status:Published
Keywords:Asteroids Ryugu Porosity Rubble Piles Parent Bodies
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 - Exploration of the Solar System
Location: Berlin-Adlershof , Köln-Porz
Institutes and Institutions:Institute of Planetary Research > Planetary Physics
Space Operations and Astronaut Training > User center for space experiments (MUSC)
Institute of Optical Sensor Systems
Deposited By: Neumann, Wladimir
Deposited On:04 Dec 2020 08:35
Last Modified:04 Dec 2020 08:35

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