Micrometeorite and Minimeteorite Ashes in Prebiotic Chemistry

Abstract

About 80% of the Cap-Prudhomme AMMs collected near the margin of the Antarctic ice sheets showed anomalous low sulfur contents (~0.1%) with regard to the value of ~ 3% measured in CM chondrites, to which about 95% of these AMMs are related. We thought first, like everybody, that sulfur, which is quoted as the most volatile of the moderately volatile elements, would have been lost upon frictional heating upon atmospheric entry. But then, why is it that Ca, which is the most refractory element, would have also been lost? Moreover, there was no size effect in the loss of S and Ca going from 200 μm to 30μm size grains. This runs against frictional heating, which increases with particle sizes. Therefore Kurat deduced that sulfur, Ca and Ni could have been preferentially lost during “cryogenic–Cweathering” effective in the first top meter of blue ice fields near the sea shore, involving the preferential leaching of carbonates, sulphates and sulfides (Maurette et al. 1992).