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Highly porous nature of a primitive asteroid revealed by thermal imaging

Author

Listed:
  • Tatsuaki Okada

    (Japan Aerospace Exploration Agency (JAXA)
    University of Tokyo)

  • Tetsuya Fukuhara

    (Rikkyo University)

  • Satoshi Tanaka

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI
    University of Tokyo)

  • Makoto Taguchi

    (Rikkyo University)

  • Takehiko Arai

    (Ashikaga University)

  • Hiroki Senshu

    (Chiba Institute of Technology)

  • Naoya Sakatani

    (Japan Aerospace Exploration Agency (JAXA))

  • Yuri Shimaki

    (Japan Aerospace Exploration Agency (JAXA))

  • Hirohide Demura

    (University of Aizu)

  • Yoshiko Ogawa

    (University of Aizu)

  • Kentaro Suko

    (University of Aizu)

  • Tomohiko Sekiguchi

    (Hokkaido University of Education)

  • Toru Kouyama

    (National Institute of Advanced Industrial Science and Technology (AIST))

  • Jun Takita

    (Hokkaido Kitami Hokuto High School)

  • Tsuneo Matsunaga

    (National Institute for Environmental Studies (NIES))

  • Takeshi Imamura

    (University of Tokyo)

  • Takehiko Wada

    (Japan Aerospace Exploration Agency (JAXA))

  • Sunao Hasegawa

    (Japan Aerospace Exploration Agency (JAXA))

  • Jörn Helbert

    (German Aerospace Center (DLR))

  • Thomas G. Müller

    (Max-Planck Institute for Extraterrestrial Physics)

  • Axel Hagermann

    (University of Stirling)

  • Jens Biele

    (German Aerospace Center (DLR))

  • Matthias Grott

    (German Aerospace Center (DLR))

  • Maximilian Hamm

    (German Aerospace Center (DLR)
    University of Potsdam)

  • Marco Delbo

    (Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange)

  • Naru Hirata

    (University of Aizu)

  • Naoyuki Hirata

    (Kobe University)

  • Yukio Yamamoto

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Seiji Sugita

    (University of Tokyo
    Chiba Institute of Technology)

  • Noriyuki Namiki

    (The Graduate University for Advanced Studies, SOKENDAI
    National Astronomical Observatory of Japan (NAOJ))

  • Kohei Kitazato

    (University of Aizu)

  • Masahiko Arakawa

    (Kobe University)

  • Shogo Tachibana

    (Japan Aerospace Exploration Agency (JAXA)
    University of Tokyo)

  • Hitoshi Ikeda

    (Japan Aerospace Exploration Agency (JAXA))

  • Masateru Ishiguro

    (Seoul National University)

  • Koji Wada

    (Chiba Institute of Technology)

  • Chikatoshi Honda

    (University of Aizu)

  • Rie Honda

    (Kochi University)

  • Yoshiaki Ishihara

    (National Institute for Environmental Studies (NIES))

  • Koji Matsumoto

    (The Graduate University for Advanced Studies, SOKENDAI
    National Astronomical Observatory of Japan (NAOJ))

  • Moe Matsuoka

    (Japan Aerospace Exploration Agency (JAXA))

  • Tatsuhiro Michikami

    (Kindai University)

  • Akira Miura

    (Japan Aerospace Exploration Agency (JAXA))

  • Tomokatsu Morota

    (University of Tokyo)

  • Hirotomo Noda

    (National Astronomical Observatory of Japan (NAOJ))

  • Rina Noguchi

    (Japan Aerospace Exploration Agency (JAXA))

  • Kazunori Ogawa

    (Kobe University
    Japan Aerospace Exploration Agency (JAXA))

  • Kei Shirai

    (Kobe University)

  • Eri Tatsumi

    (University of Tokyo
    Instituto de Astrofísica de Canarias, University of La Laguna, La Laguna)

  • Hikaru Yabuta

    (Hiroshima University)

  • Yasuhiro Yokota

    (Japan Aerospace Exploration Agency (JAXA))

  • Manabu Yamada

    (Chiba Institute of Technology)

  • Masanao Abe

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Masahiko Hayakawa

    (Japan Aerospace Exploration Agency (JAXA))

  • Takahiro Iwata

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Masanobu Ozaki

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Hajime Yano

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Satoshi Hosoda

    (Japan Aerospace Exploration Agency (JAXA))

  • Osamu Mori

    (Japan Aerospace Exploration Agency (JAXA))

  • Hirotaka Sawada

    (Japan Aerospace Exploration Agency (JAXA))

  • Takanobu Shimada

    (Japan Aerospace Exploration Agency (JAXA))

  • Hiroshi Takeuchi

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Ryudo Tsukizaki

    (Japan Aerospace Exploration Agency (JAXA))

  • Atsushi Fujii

    (Japan Aerospace Exploration Agency (JAXA))

  • Chikako Hirose

    (Japan Aerospace Exploration Agency (JAXA))

  • Shota Kikuchi

    (Japan Aerospace Exploration Agency (JAXA))

  • Yuya Mimasu

    (Japan Aerospace Exploration Agency (JAXA))

  • Naoko Ogawa

    (Japan Aerospace Exploration Agency (JAXA)
    Japan Aerospace Exploration Agency (JAXA))

  • Go Ono

    (Japan Aerospace Exploration Agency (JAXA))

  • Tadateru Takahashi

    (Japan Aerospace Exploration Agency (JAXA)
    NEC Corporation)

  • Yuto Takei

    (Japan Aerospace Exploration Agency (JAXA))

  • Tomohiro Yamaguchi

    (Japan Aerospace Exploration Agency (JAXA)
    Mitsubishi Electric Corporation)

  • Kent Yoshikawa

    (Japan Aerospace Exploration Agency (JAXA))

  • Fuyuto Terui

    (Japan Aerospace Exploration Agency (JAXA))

  • Takanao Saiki

    (Japan Aerospace Exploration Agency (JAXA))

  • Satoru Nakazawa

    (Japan Aerospace Exploration Agency (JAXA))

  • Makoto Yoshikawa

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

  • Seiichiro Watanabe

    (Japan Aerospace Exploration Agency (JAXA)
    Nagoya University)

  • Yuichi Tsuda

    (Japan Aerospace Exploration Agency (JAXA)
    The Graduate University for Advanced Studies, SOKENDAI)

Abstract

Carbonaceous (C-type) asteroids1 are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites2,3 and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth’s atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)4 onboard the spacecraft Hayabusa25, indicating that the asteroid’s boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m−2 s−0.5 K−1 (300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites6 and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect7,8. We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites6. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity9 of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies10.

Suggested Citation

  • Tatsuaki Okada & Tetsuya Fukuhara & Satoshi Tanaka & Makoto Taguchi & Takehiko Arai & Hiroki Senshu & Naoya Sakatani & Yuri Shimaki & Hirohide Demura & Yoshiko Ogawa & Kentaro Suko & Tomohiko Sekiguch, 2020. "Highly porous nature of a primitive asteroid revealed by thermal imaging," Nature, Nature, vol. 579(7800), pages 518-522, March.
  • Handle: RePEc:nat:nature:v:579:y:2020:i:7800:d:10.1038_s41586-020-2102-6
    DOI: 10.1038/s41586-020-2102-6
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    Cited by:

    1. Yoshinori Takano & Hiroshi Naraoka & Jason P. Dworkin & Toshiki Koga & Kazunori Sasaki & Hajime Sato & Yasuhiro Oba & Nanako O. Ogawa & Toshihiro Yoshimura & Kenji Hamase & Naohiko Ohkouchi & Eric T. , 2024. "Primordial aqueous alteration recorded in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu," Nature Communications, Nature, vol. 15(1), pages 1-15, December.
    2. M. Pajola & F. Tusberti & A. Lucchetti & O. Barnouin & S. Cambioni & C. M. Ernst & E. Dotto & R. T. Daly & G. Poggiali & M. Hirabayashi & R. Nakano & E. Mazzotta Epifani & N. L. Chabot & V. Corte & A., 2024. "Evidence for multi-fragmentation and mass shedding of boulders on rubble-pile binary asteroid system (65803) Didymos," Nature Communications, Nature, vol. 15(1), pages 1-13, December.

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