Isotopic studies of megacryometeors in western India.

Four unusually large ice-stones (megacryometeors) weighing several kilograms fell in western India during October-November 2010. Samples were retrieved from three fall events. To study the origin and formation of these megacryometeors, d 18O, d D, chemical composition and ?-activity were measured. The range of d 18O-d D is similar to the local meteoric water, suggesting origin from local atmospheric water vapour. The relative humidity at ~4 km altitude was higher during a few days before and after the fall. No ?- activity from cosmogenic radionuclides such as 26Al could be detected in the inherent dust. These studies indicate terrestrial origin of these megacryometeors. [ABSTRACT FROM AUTHOR]