Earth's magnetosphere governs speed of solar wind on lunar nearside
A study of lunar samples from China's Chang'e 6 mission reveals that Earth's magnetosphere acts as a speed governor for solar wind on the moon's nearside. Researchers found that solar wind particles are significantly decelerated before hitting the side of the moon facing Earth, a phenomenon preserved in the lunar soil's noble gas record.
Why it matters
This discovery provides new insights into the long-term interaction between Earth's magnetic field and the solar environment, utilizing the moon as a geological time capsule.
The farside of the moon receives solar wind particles at nearly full speed, while its Earth-facing side is hit by the same wind after it has been slowed by nearly half, according to a study published recently in the journal Nature Geoscience.
The discovery, based on the first-of-its-kind noble gas analysis of lunar farside samples returned by China's Chang'e 6 mission in 2024, shows that Earth's magnetosphere acts as a natural "speed governor" — deflecting and decelerating solar wind before it reaches the nearside — and that the effect is permanently locked into the soil's noble gas record.
The solar wind — a continuous flow of charged particles from the sun — is the primary carrier of volatile elements across the solar system. On Earth, a strong global magnetic field blocks most of this inflow, while ongoing geological activity continuously erases the planet's ancient magnetic signatures.
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