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[Kyodo News Agency, December 20th]A team from the Japan Aerospace Exploration Agency (JAXA) and Kyoto University published an article in the British professional magazine “Nature Astronomy” on the 19th, stating that on the asteroid “Ryugu”, there was once a small The impact of the meteorite caused the surface to dissolve and lose moisture, resulting in a change in appearance, somewhat resembling that of a human being sunburned. The team analyzed a total of 0.7 mg of sand samples (about 800 grains) collected by the probe “Hayabusa 2”. This change is called “space weathering”. For the samples of the asteroid “Itokawa” collected by the first-generation “Hayabusa” and the “Ryugu” type, the correlation analysis has been advanced. On Ryugu, more surface-dissolved sand samples were found than on Itokawa. Noguchi Takaaki (Meteorites), a professor at Kyoto University, speculated that “different types of asteroids have different “solarization” conditions, which is surprising. The rocks of “Ryugu” have many gaps in the middle, and the particles may be prone to friction and heat when the meteorite hits. What is dissolved is the area from the surface to the depth of 0.002 to 0.003 mm. The whole is left with many small holes that resemble undulations or bubble bursts. It is said that it can be considered as the trace of the heated water that has been turned into water vapor and escaped. The team also found microporous layers on the smooth surface, which they think are weathered by the flow of plasma (solar wind) blowing from the sun. (use up)
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