K-Ar dating of lunar fines - Apollo 12, Apollo 14, and Luna 16.

K-Ar ages were determined on a 6-in. double-focus mass spectrometer in fines of less than 1 mm from Apollo 14 and 16, and Luna 16 lunar soil samples. Age estimates of about 2.8 AE and about 4.0 AE are suggested for the two low-K components whose presence in the samples must be assumed to accommodate the age data. An average value of 0.1849 plus or minus 0.0008 was obtained for the Ar-18/Ar-36 ratio in the solar wind from ordinate intercept correlations for the Apollo 14 and Luna 16 samples. Cosmic ray exposure ages were close to 440 m.y. for both Apollo 14 samples and close to 840 m.y. for both Luna 16 samples.