The Sun continually emits a flux of electrically charged particles into space. This is termed the solar wind The earth's magnetic field prevents these particles from reaching the earth's surface. The Moon is outside the Earth's magnetic field for most of each month and has a negligible atmosphere, allowing solar-wind particles to reach the Moon's surface. The Solar Wind Composition Experiment was deployed on the Moon to study solar wind.
Solar wind composition method: It consists of an aluminum foil sheet that is set up on the pole facing the sun. It is 1.4 meters by 0.3 meters in size. The foil was exposed to sun for 77 minutes thus allowing the solar wind particles to embed themselves into the foil. The foil was returned to earth for laboratory analysis. The isotopes of the light noble gases were measured, including helium-3, helium-4, neon-20, neon-21, neon-22, and argon-36.