Fresh evidence from China’s Chang’e-6 mission is helping explain why the Moon’s two sides record solar wind exposure differently, according to ScienceDaily and a study published in Nature Geoscience.
The Moon has been exposed to the solar wind for billions of years, but researchers say the particles do not reach both hemispheres in the same way. The near side and far side appear to receive particles with different speeds and energies.
The new analysis focused on 1.935 grams of regolith returned from the Moon’s far side in the South Pole Aitken basin. A team led by the Institute of Geology and Geophysics of the Chinese Academy of Sciences examined noble gases in the material, including helium, neon, argon, krypton and xenon.
One of the clearest differences involved neon isotopes. The Chang’e-6 sample showed a lower 20 Ne/22 Ne ratio than earlier near-side samples, which the researchers say points to stronger isotopic fractionation on the far side and deeper penetration by faster particles.
The team says the most likely explanation is Earth’s magnetosphere. As the Moon passes through the magnetosheath around Earth, the solar wind can slow down, affecting the near side more than the far side. The researchers say the far-side samples provide the first direct physical evidence that Earth’s magnetosphere changes the speed of solar wind particles reaching different parts of the Moon.
