May 8, 2020 (JST)

Japan Aerospace Exploration Agency (JAXA)
The University of Tokyo
Nagoya University
Chiba Institute of Technology
Kochi University
Rikkyo University
University of Aizu
Meiji University

We hereby announce that a paper presenting the results of research based on asteroid Ryugu exploration activities by Asteroid Explorer “Hayabusa2” was published in the electronic version of the US scientific magazine Science on May 7, 2020 (May 8, JST).

The following shows the outline of the paper.

On February 22, 2019 (JST), Asteroid Explorer “Hayabusa2” successfully made its first touchdown on Ryugu for the purpose of collecting a sample. The super-high-resolution images obtained at the time of touchdown revealed that many rocks and numerous dark red particles, which may have been attached on rock surfaces and cracks within rocks, were kicked up by the thruster injection as well as by the bullet fired into the asteroid surface upon touchdown. Moreover, observations on the crater retention age and the color of subsurface materials excavated by impact cratering revealed that dark red materials are distributed in a surface layer with the thickness of a few meters entirely across Ryugu and that these dark red materials on the Ryugu surface have been burnt by the Sun and thereby altered between 8 million years ago and 300,000 years ago. This indicates that Ryugu was once in an orbit closer to the Sun. Moreover, on the surface of the touchdown point, there are also unaltered materials colored in bright-blue, in addition to the dark red materials. The collected sample contains both the unaltered and altered substances.

MOROTA Tomokatsu et al., Sample collection from asteroid 162173 Ryugu by Hayabusa2: implications for surface evolution. Science 08 May 2020.
DOI: 10.1126/science.aaz6306