Small particles of solid matter between the planets of the Solar System. They are produced mainly by collisions between asteroids and by the break-up of comets, but some enter the Solar System from interstellar space. There are trails of dust grains along the orbits of comets and asteroids, which are experienced as meteor streams if they cross the Earth’s path. Interplanetary dust grains can also be detected when they scatter sunlight to form the zodiacal light, and by the small amount of infrared radiation they produce.