Originating from comets, asteroids, and other Solar System or interstellar bodies, micrometeorites are the remnants of the cosmic dust flux to the Earth. Each day, roughly 100 tonnes of these cosmic dust particles enter the Earth’s atmosphere. Large particles or those with high entry speeds experience significant drag in the atmosphere and can often be seen as shooting stars. Smaller particles or those with low entry speeds may survive the atmospheric entry as micrometeorites. Contrary to meteorite fragments, micrometeorites were thus already small upon atmospheric entry, and are commonly <0.5 mm in size. Isotopic studies have shown that they are predominantly related to carbonaceous chondrites, making them distinct from larger meteorites that commonly belong to the ordinary chondrites.

 

These cosmic visitors steadily rain down onto the Earth’s surface with a constant flux of roughly one micrometeorite per square meter annually. Since the 1980s, micrometeorites have frequently been collected from various remote locations such as Greenland, Antarctica, the deep sea, and deserts, where the influx of terrestrial and anthropogenic particles is low. Only recently, micrometeorites have been found in significant numbers in inhabited areas by searching on rooftops (Genge et al. 2017; Suttle et al. 2021; Jonker et al. 2023). These rooftop micrometeorites have opened up new doorways for scientists to study the modern-day flux of cosmic dust, but are no longer exclusively in the hands of research institutions. Now, these miniature gems from outer space are slowly becoming available for private collectors and are a valuable addition to any meteorite collection.