A Piece of Interplanetary Dust

Explanation: The dust that pervades our Solar System is not the dust that pervades our homes. Solar System dust comes from comets and asteroids , whereas house dust is most likely lint or dead cells. Pictured above is a piece of interplanetary dust caught by a high-flying U2 -type aircraft. It likely originates in the early days of our Solar System , being stored and later ejected by a passing comet . The particle is composed of glass , carbon , and a conglomeration of silicate mineral grains . It measures only 10 microns across, a tenth the width of a typical human hair . NASA's STARDUST mission, launched in 1999, is scheduled to pass through the tail of Comet Wild 2 in 2004 and return many more interstellar dust samples to Earth in 2006.