BE-10 AND AL-26 IN INDIVIDUAL COSMIC SPHERULES FROM ANTARCTICA

We present data for the cosmogenic nuclides Be-10 and Al-26 in a suite of 24 estraterrestrial spherules, collected from Antarctic moraines a nd deep sea sediments. All of the IO large spherules collected in glac ial till at Lewis Cliff are extraterrestrial. As in earlier work, the great majority of particles show prominent solar cosmic-ray (SCR) prod uction of Al-26, indicating bombardment ages on the order of 10(6) yea rs or even longer. These long ages are in direct contradiction to mode l ages for small particles in the inner Solar System and may require r econsideration of models of small particle lifetimes. A small fraction of the particles so far measured (6/42) possess cosmogenic radionucli de patterns consistent with predictions for meteoroid spall droplets. We believe that most of the spherules were bombarded in space primaril y as bodies not much larger than their present size. The content of in situ produced Be-10 and Al-26 in quart, pebbles in the same moraine s uggests that these spherules may have on average a significant terrest rial age.