Cosmic dust grain 11 microns in diameter.
Many tons of dust grains, including samples of asteroids and comets, fall from space onto the Earth's atmosphere each day. An even larger amount of spacecraft debris particulates reenter the Earth's atmosphere every day. Once in the stratosphere this ‘cosmic dust’ and spacecraft debris joins terrestrial particles such as volcanic ash, windborne desert dust and pollen grains. High flying aircraft with special sticky collectors capture this dust as it falls through the stratosphere, before it becomes mixed with Earth dust. The ultra-clean Cosmic Dust Laboratory, established in 1981 to handle particles one-tenth the diameter of a human hair, curates over thousands of cosmic dust particles and distributes samples to investigators worldwide.
Cosmic dust grains include samples from comets and asteroids, containing material in the same condition as when the solar system began to form. Unlike meteorites, cosmic dust samples all bodies in the solar system. Examination of cosmic dust also reveals much about the populations of interplanetary dust and orbital debris particles in low-Earth orbit. Such information is useful to engineers planning protection of spacecraft against damage from high-velocity dust grains. The terrestrial dust and spacecraft debris particles are of considerable interest to atmospheric scientists and climatologists, since they influence some global atmospheric reactions.
The majority of stratospheric collections are made at random times. However, ever since Dermott and Liou (1994) proposed that there should be enhancements in certain types of asteroidal dust at certain times of the year, we have endeavored to build up a collection of collection surfaces targeted at different times throughout the year. Typically, these take the form of collectors, both large and small, flown for one calendar month only. Inspection of our holdings of collection surfaces will reveal many of these surfaces. We have made targeted collections of the stratosphere in attempts to collect dust from specific comets (Tempel-Tuttle, Giabobini-Zinner, and Grigg-Skjellerup), as well as dust from asteroid families. We consider these efforts to be long shots, since the enhancements of the comet dust over background extraterrestrial material are not terribly large. Still we have made a special effort to provide these collection surfaces to the community, since the potential payoffs from successfully locating comet dust from a known source are so great. We will continue to attempt to collect dust from specific solar system bodies, as opportunities arise.