micrometeorite

Micrometeorites are tiny extraterrestrial particles that reach the Earth's surface. They are typically defined as meteorites no larger than about 1 millimeter in diameter, though some definitions extend to a few millimeters. Their small size makes them far more numerous than larger meteorites and a major component of the ongoing influx of cosmic dust to Earth.

Most micrometeorites originate from comets or asteroids and from the broader population of interplanetary dust. As they enter the atmosphere, they experience rapid heating and melting, and often cool into glassy spherules or partly melted fragments. Many carry a fused outer crust and may contain iron-nickel metal droplets or silicate minerals, reflecting their diverse origins and shock histories.

Collection and study typically focus on pristine specimens recovered from polar regions, Antarctic ice and sediments, or from deep-sea sediments and clean collection substrates. To avoid terrestrial contamination, researchers use careful handling and analytical techniques, including electron microscopy and isotopic measurements, to characterize composition, texture, and exposure histories.

Significance in science arises from their potential to reveal information about the composition of the early solar system, the makeup of comets and asteroids, and the processes that governed dust creation in interplanetary space. Micrometeorites complement larger meteorites and interplanetary dust particles (IDPs) by providing a high-volume record of the tiny end of the cosmic dust spectrum, helping to illuminate solar system evolution and the flux of material to Earth.