A joint research team (JAXA Space Science Institute, Nagoya University) led by Professor Kentaro Terada of the Graduate School of Science, Osaka University, uses a plasma observation device mounted on the lunar orbiting satellite "Kaguya" and flows out of the Earth's gravitational sphere due to solar activity. We succeeded in directly observing that the oxygen generated reached the moon 38 km away.

 The earth is protected from the solar wind and cosmic rays by the earth's magnetic field.On the night side opposite to the Sun, the Earth's magnetic field is stretched like a comet's tail, creating a windsock-shaped magnetosphere with a sheet of hot plasma in its center. There is an area (plasma sheet).

 The research team analyzed the plasma data of 100km above the moon surface acquired by the plasma observation device installed in "Kaguya".We found that high-energy oxygen ions appear only when the moon and "Kaguya" cross the plasma sheet.Until now, it was known that oxygen ions leaked from the polar regions of the earth into outer space, but this time, it is known in the world that oxygen ions are being carried to the surface of the moon 38 km away as "earth wind". It was revealed for the first time by observation.

 The oxygen ion detected this time had high energy (1-10 kiloelectronvolt [keV]).Oxygen ions of such energy can penetrate to a depth of several tens of nanometers of metal particles.This is a very important finding in understanding the complex oxygen isotope composition of the lunar topsoil, which has been a mystery for many years.

 This discovery reveals that under the influence of solar activity, the Earth and the Moon have been mechanically and chemically interacting and co-evolving as a correlated system for billions of years.In the future, it may have a great impact on many people's views of nature and science.

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