The solar wind as deduced from lunar samples

Lunar surface samples, which have been exposed to the solar wind, can be used to obtain information on the recent and past solar wind. Some of the more important conclusions reached are: The D/H ratio in the solar wind is smaller than 0.000003. The isotopic composition of C, Ar (except Ar-40), and Kr in the solar wind and on the earth are the same within approximately plus or minus 3%. Terrestrial Ne is enriched in the heavier isotopes relative to solar wind Ne. The average solar wind flux in the past was probably higher than at present. The average solar wind energy has varied in the past; however, no long time trend is apparent. Evidence for a secular decrease of the He-4/He-3 ratio with time exists.