Exploration activities by the asteroid explorer "Hayabusa2" revealed that the asteroid Ryugu is a celestial body made of matter full of gaps.International collaboration with Aerospace Research and Development Organization (JAXA), Rikkyo University, Ashikaga University, Chiba Institute of Technology, University of Aizu, Hokkaido University of Education, Nagoya University, German Aerospace Center (DLR), Max-Planck Institute for Extraterrestrial Physics University of Stirling, etc. The research team announced.

 Ryugu is classified as a C-type (carbonaceous) asteroid considered to be a primitive celestial body, and is considered to be a "fossil" that preserves the primitive material at the time of the formation of the solar system 46 billion years ago.However, little is known about what kind of matter is formed by gathering and how it is a celestial body.

 This research team used the mid-infrared camera TIR mounted on the Hayabusa2, that is, thermography, to perform the first global imaging of a C-type asteroid in history for one continuous rotation, and analyzed the acquired data. ..As a result, it was found that Ryugu was covered with a substance having extremely low thermal inertia (easy to warm and cool), and was extremely squishy (high voids) and had severe irregularities.In addition, since the surface rock mass and the surrounding soil have almost the same temperature and the diurnal temperature changes are almost the same and small, both the rock mass and the surrounding soil are squishy and are thermally equivalent substances. all right.

 On the other hand, several rock masses called cold spots, whose temperature is 20 degrees or more lower than the surroundings, were discovered.It is said that this may originate from a substance that has been consolidated in the center of the parent object during the formation process of Ryugu, or a celestial body that has collided with the parent object.

 Rocky celestial bodies such as the Earth are thought to have grown and formed by the gathering of fluffy dust in the early solar system, but the asteroid Ryugu, which is full of gaps, may be a celestial body that embodies the process. This study suggests.

Paper information:[Nature] Highly porous nature of a primitive asteroid revealed by thermal imaging

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