Occurrence and composition of relict minerals in micrometeorites from Greenland and Antarctica - implications for their origins

The mineralogy and chemistry of 161 micrometeorites from Greenland (100-200 μm in size) and 66 micrometeorites from Antarctica (50-100 μm in size) were studied in order to obtain information about the origin of micrometeorites. Within 66 of these 227 particles, 140 relict olivines and 84 relict pyroxenes were found. In addition, other relict minerals were identified, including perovskite, chromite, Fe,Ni-metal, magnetite and sulfides. The textures of micrometeorites showing relict minerals range from finegrained porous particles to spherical particles. Relict minerals escaped melting during atmospheric heating and, therefore, they are the best candidates for a comparable study with other extraterrestrial material. Based on our study of relict grains from micrometeorites, we suggest a close relationship of most of the particles to various types of carbonaceous chondrites. Only a few particles are probably related to ordinary chondrites. We did not find any relict grains that may be related to minerals common in achondrites and stony iron meteorites. Since the majority of asteroids appear to consist of materials related to carbonaceous chondrites, we conclude that, statistically, micrometeorites with relict grains in the studied size range of 50-200 μm represent much better the abundance of distinct types of asteroids than the abundance of distinct groups of meteorites as revealed by the statistics of modern falls.