Researchers discover asteroidal ice fossils in primitive meteorite (Press Release)
- Release Date
- 21 Nov, 2019
- BL47XU (HAXPES / uCT)
November 21, 2019
Tohoku university
Kyoto university
Ritsumeikan university
Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Japan Synchrotron Radiation Research Institute (JASRI)
Researcher undertaken at Tohoku University has discovered fossil asteroidal ice within a meteorite. Performing a high-resolution CT imaging of a primitive, 4.6 billion years old meteorite, researchers discovered µm-sized ultra-porous regions inside the meteorite. The porous texture is highly likely to have formed when the previously ice-filled pore spaces disappeared, suggesting that the ultra-porous regions represent primordial ice fossils. Based on the discovery, the research team proposed a new practical model indicating that the meteorite parent body (a planetesimal) formed by icy dust agglomeration through radial migration from the outer to inner regions of the early Solar System, across the H2o snow line. Their findings provide further insights into the formation of asteroids in the early Solar System. Asteroids formed in the outer region of the H2o snow line are thought to have contained some ice upon formation. It is known that there exists a large number of meteorites seeming to have experienced aqueous alteration caused by ice melting in asteroids. However, researchers have yet to discover how the primordial ice responsible for the aqueous alteration was distributed to the meteorite parent bodies. The researchers examined meteorite Acfer 094 and discovered fossil asteroidal ice within it. Based on their microscopic observations, they hypothesize that the ice was originally formed by the sintering of fluffy icy dust around the H2o snow line and subsequently incorporated into the meteorite parent body. The sintering process converted the fluffy icy dust into solid ice-silicate aggregates which were resistant to compaction in the meteorite parent body. The incorporation of the aggregates into the meteorite parent body occurred around the H2o snow line during the radial migration of the parent body from the outer to inner regions of the early Solar System. After the incorporation, ice in the aggregates disappeared when an increase in temperature caused evaporation and/or melting. This resulted in the formation of ultra-porous regions inside the meteorites. These findings are important in terms of providing new insight to understanding of asteroid formation in the early Solar System. The details are described in a paper published by Science Advances online. Publication Details: |
Image
Fig. 1: CT slice image of a box shaped meteorite sample at 8 keV. Porous region containing abundant pores (dark color) is indicated by a white dashed line. The porous region was formed by removal of ice previously filling pore spaces. Grains with dark gray and white colors are silicates and Fe-rich sulfides, respectively.
Copyright: Megumi Matsumoto et al.
Fig. 2: Fluffy icy dust were converted into solid ice-silicate aggregates by sintering process occurred around the snow line in the early Solar System.
Copyright: Megumi Matsumoto et al.
Fig. 3: (A) Electron microscope image of a fossil asteroidal ice on the polished surface of the Acfer 094 meteorite sample. (B) Electron microscope image of the whole meteorite sample. (C) Illustration showing the distribution of fossil asteroidal ice in the meteorite sample.
Copyright: Megumi Matsumoto et al.
Fig. 4: Schematic illustration of the Acfer 094 parent body formation model.
Copyright: Megumi Matsumoto et al.
Collaborating institutions:
Tohoku university, Kyoto university, Ritsumeikan university, Guangzhou Institute of Geochemistry, Japan Aerospace Exploration Agency (JAXA), National Astronomical Observatory of Japan (NAOJ), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Marine Works Japan Ltd., Japan Synchrotron Radiation Research Institute (JASRI), National Institute of Advanced Industrial Science and Technology (AIST), Natural History Museum in London (NHM).
This study was supported by grant-in-aid No. 15H05695 for A. Tsuchiyama and No. 18H04468 and 18K18795 for M. Ito from the Japan Society for the Promotion of Science.
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