Solid State Studies of the Radiation History of Lunar Samples

Abstract

Particle track densities up to > 3 x 10⁹ per square centimeter have been measured in different samples. Rocks 17, 47, 57, and 58 have VH (Z >22) galactic cosmic ray ages of 11, 14, 28, and 13 x 10⁶ years, respectively. Rock 57 has a calculated erosion rate of 10^-7 centimeter per year. Near-surface track versus depth data in rock 17 can be fit with solar flare particles that have a differential energy spectrum aE^-3; lunar samples can be used to study the history of solar activity. The uranium in the crystalline rocks occurs principally in small regions <10 to ∼100 micrometers in size. The (low) thermoluminescence of the fines increases with depth in core 10004. With one possible exception, x-ray studies have not shown pronounced radiation damage effects. The total energy release upon heating is small up to 900°C and occurs in three broad regions.