On the question of the 40Ar excess in lunar soils

The retrapping mechanism proposed to explain the excess 40Ar in lunar soil samples is discussed. Questions arise from the following experimental facts. Gas release in linear heating experiments is similar for excess 40Ar and for solar wind 36Ar, the latter having much higher implantation energy. In feldspar and olivine-pyroxene separates from a lunar soil the 40Ar/36Ar ratio of surface correlated argon is different. In feldspar grain size separates, potassium and 36Ar appear linearly correlated. Possible influences of the Moon's ancient magnetic properties for the efficiency of the retrapping mechanism are discussed. Arguments supporting the notion of a second process, the transient K coating, are presented. The problem remains unsettled and further studies are needed. (author)