What are interplanetary dust particles?
Interplanetary dust particles are tiny grains collected in Earth's stratosphere by high-flying aircraft; many come from comets and are among the most primitive materials known.
Interplanetary dust particles, or IDPs, are microscopic grains, usually 5 to 50 micrometres across, that drift down through Earth's upper atmosphere. Unlike micrometeorites found on the ground, many IDPs reach Earth without melting, because they are small and decelerate gently high in the atmosphere.
Since the 1970s, NASA has collected IDPs using high-altitude aircraft flying at about 20 kilometres, above most terrestrial dust. Sticky collector plates mounted on the wings catch the particles, which are then curated in clean laboratories.
IDPs come in two broad kinds. Chondritic porous IDPs are fluffy aggregates of tiny grains of glass, minerals and organic matter. They are thought to come mainly from comets and are among the most primitive materials in the Solar System. Some contain abundant presolar grains, organic material with unusual isotopes, and GEMS, glass with embedded metal and sulfides, which may be interstellar dust. Chondritic smooth IDPs are more compact and contain water-bearing minerals, like carbonaceous chondrites, and are thought to come from asteroids.
IDPs are valuable because they sample bodies, such as comets, not represented among meteorites. Comparing them with dust returned from comet Wild 2 by the Stardust mission and with samples from asteroids Ryugu and Bennu helps scientists understand the variety of small bodies in the Solar System.
IDPs can be timed to meteor showers: aircraft flights during showers, such as one timed with the Draconids, have attempted to collect dust from specific comets.