Beryllium-10 from the Sun

Beryltium-10 (Be-10) in excess of that expected from in situ cosmic ray spa llation reactions is present in lunar surface soil 78481; its presence was revealed with a sequential leaching technique. This excess Be-10, represent ing only 0.7 to 1.1% of the total Be-10 inventory, is associated with surfa ce layers (<1 micrometer) of the mineral grains composing 78481. This exces s Be-10 and its association with surficial layers corresponds to (1.9<plus/ minus>0.8) x 10(8) atoms per square centimeter, requiring a Be-10 implantat ion rate of (2.9 +/-1.2) x 10(-6) atoms per square centimeter per second on the surface of the Moon. The most likely site for the production of this e xcess Be-10 is the Sun's atmosphere. The Be-10 is entrained into the solar wind and transported to the lunar surface.