EVIDENCE IN A GLASSY COSMIC SPHERULE FROM ANTARCTICA FOR GRAZING-INCIDENCE ENCOUNTERS WITH THE EARTHS ATMOSPHERE

Cosmic dust accreted by the Earth can be extensively reprocessed durin g atmospheric encounters. The textures and compositions of reprocessed material provide important constraints by which the processes affecti ng extraterrestrial matter in the Earth's atmosphere can be better und erstood. Here we report results on an unusual Antarctic glassy cosmic spherule that demonstrates strong textural evidence for at least two g razing incidence encounters with the Earth's atmosphere prior to final reentry. The particle consists of a central glassy core with four per ipheral glass lobes that transect a silicate particle rim. The texture of the particle confirms previous theoretical speculations that some high velocity, low incidence angle interplanetary particles experience numerous encounters with the Earth's atmosphere and also indicates th at micrometeorites demonstrating multiple melting episodes should be i nterpreted with caution.