NEW INTERPRETATION OF THE BE-10 AND AL-26 CONTENT IN COSMIC SPHERULES

The observed concentrations of cosmogenic nuclides in extraterrestrial matter are usually interpreted in terms of the exposure history of th e irradiated specimen or in terms of the history of the cosmic radiati on itself, For small meteorites in the microgram mass range we present a theoretical approach which allows a new interpretation of the measu red concentrations. In particular, we show how to determine the size d istribution of the interplanetary dust and how to investigate the rela ted phenomena (radiation pressure, mutual collisions, atmospheric entr y). For this, the concentrations of the radioisotopes Be-10 and Al-26 contained in spherules from deep sea sediments were measured by means of the AMS technique. Due to the small sample size, the carrier amount was successfully kept very low: around 50 mu g for Be and between 100 and 200 mu g for Al.