Micrometeorites

The Earth accretes some 40,000 tonnes of extraterrestrial material each year. Most of this is interplanetary dust produced by collisions and evaporation of rocky and icy bodies in the Solar System. A fraction of this dust survives hypervelocity impact with the Earth’s upper atmosphere and is collected at the Earth’s surface in the form of microscopic particles (~2 mm) called micrometeorites. Significant quantities of micrometeorites are recovered mainly from deep-sea sediments, and snow, ice and loose sediments in polar areas. Micrometeorites provide samples of a variety of dust-producing bodies in the Solar System for laboratory analysis, most notably primitive asteroids and comets which allow exploration of the first stages in the evolution of the protoplanetary disk. Furthermore, the systematic study of unbiased and time-constrained micrometeorite collections allows investigation of the cycles of extraterrestrial input to the global geochemical budget of planet Earth, including its bearing on the emergence of life. Lastly, knowledge of the physical and compositional properties of micrometeorites provides constraints for modelling the source regions and dynamic evolution of the cosmic-dust complex in the near-Earth space, as well as for assessing the potential hazard of dust in the vicinity of the Earth to space activities. This work provides basic information on micrometeoroid production in space and delivery to Earth, atmospheric entry and micrometeorite collections. It gives an overview of current knowledge of the diversity of micrometeorites in terms of their nature and origin, highlighting recent advances in the identification of new types and in the quantification of the flux of extraterrestrial matter to Earth.