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July 2, 2019
Ibaraki University
The University of Tokyo

Laboratory analysis of meteorites have shown evidence that
asteroids migrated towards the asteroid belt from the outer solar system
-The research team succeeded in determining where asteroids formed based on the amounts of dry ice inferred from carbonate minerals in meteorites -

The international research team including W. Fujiya (Faculty of Science, Ibaraki University), P. Hoppe (Max Planck Institute for Chemistry in Germany), T. Ushikubo (Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology: JAMSTEC), and Y. Sano (Atmosphere and Ocean Research Institute, The University of Tokyo) estimated the amounts of dry ice (solid carbon dioxide) contained in asteroids based on analyses of carbonate minerals in meteorites. The experimental data demonstrate for the first time that some asteroids, which are currently located in the asteroid belt, originally formed in the outer solar system (beyond Jupiter's orbit), and that they must have later migrated inwards to their current orbit.

Most asteroids are currently concentrated in the asteroid belt between the orbits of Mars and Jupiter. Theoretical models have proposed that some of these asteroids originally formed in the cold outer solar system and were scattered and transported to their current locations in response to orbital migration of the giant planets.

These models can be tested by analyzing pieces of asteroids that fall to Earth as meteorites. The abundance of volatile species in these meteorites, such as carbon compounds, can be used a proxy for the formation temperature of asteroids and so distance from the sun.

In the present work, the team analyzed the carbon isotope ratios (ratios of carbon-13 to carbon-12) of abundant carbonate minerals in the Tagish Lake meteorite (which fell in Tagish Lake, located in the western part of Canada, in 2000). They found that carbon in the carbonate minerals was likely derived from dry ice contained in the meteorite’s parent asteroid. Furthermore, the team found that the estimated carbon isotope ratio of the dry ice and the ratio of carbon dioxide to water in the parent body were both similar to ice in comets. These results indicate that the parent body of the Tagish Lake meteorite, probably a D-type asteroid, formed in an extremely low temperature environment, farther from the sun than Jupiter, where carbon dioxide could have condensed. This D-type asteroid subsequently migrated to the asteroid belt. These are the first experimental results to have determined the process of the formation of an asteroid and its orbital evolution.

The team’s results show that carbonate minerals in meteorites can reveal the abundance of dry ice in their parent asteroid, which is in turn an good indicator of ambient temperature. Thus, it is expected that carbonate in meteorites will further help to elucidate the formation processes of asteroids. In addition, the similarity between D-type asteroids and comets indicates that information about comets as well as trans-Neptunian objects can be obtained by studying D-type asteroids, and this information will be important for future planetary exploration missions.

The results will be published in the international academic journal, Nature Astronomy on July 2 (JST), 2019.

Title: Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites
Authors: W. Fujiya1, P. Hoppe2, T. Ushikubo3, K. Fukuda4,9, P. Lindgren5, M. R. Lee6, M. Koike7,10, K. Shirai8,11 and Y. Sano7
Affiliations: 1 Faculty of Science, Ibaraki University, 2 Max Planck Institute for Chemistry 3 Kochi Institute for Core Sample Research, JAMSTEC 4 Department of Earth and Planetary Science, The University of Tokyo 5 Department of Geology, Lund University 6 School of Geographical and Earth Sciences, University of Glasgow 7 Atmosphere and Ocean Research Institute, The University of Tokyo, 8 International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo 9 (Current) Department of Geoscience, University of Wisconsin-Madison 10 (Current): Department of Solar System Science, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency 11 (Current) Atmosphere and Ocean Research Institute, The University of Tokyo


(For this study)
Wataru Fujiya, Assistant Professor, Ibaraki University
Takeyuki Ushikubo, Research Scientist, Kochi Institute for Core Sample Research
Yuji Sano, Professor, Atmosphere and Ocean Research Institute, The University of Tokyo
(For press release)
Public Relations Office, Ibaraki University
Public Relations Section, Marine Science and Technology Strategy Department
Public Relations Office, Atmosphere and Ocean Research Institute, The University of Tokyo
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