Mn-53 in the Apollo 15 and 16 drill stems - Evidence for surface mixing

The activity of cosmic ray produced Mn-53 has been measured in a series of samples from the upper 10 cm of the Apollo 15 and 16 drill stems. The activity profiles for both cores indicate disturbance to depths of about 3 g/sq cm within the last 6 m.y. In at least one case (Apollo 16) the soil has been gardened to at least 14 g/sq cm within the last 10 m.y., and material from the upper less than 2 g/sq cm has been buried to 14 g/sq cm by this gardening. The results for the Apollo 15 core are compatible with a wide variety of possible histories including loss or gain of material.