Between the planets of our solar system, there is matter, mainly dust and gas. It is called interplanetary matter.
Contrary to earlier opinions, planetoids, comets and asteroids are no longer considered to be part of this category. It is the matter from the corona, particles from the zodiacal light, as well as finely distributed dust and gas that once belonged to the atmospheres of the individual planets.
The main part of the interplanetary matter exists as an immense dust cloud surrounding the Sun and planets. The size of the particles ranges from 0.001 to 0.1 millimeters. Calculations have shown that all the dust together would only be a little more than a billionth of the mass of the Earth.
The particles of the zodiacal light form a cloud of dust and gas surrounding the Sun. The zodiacal light can be seen as a lightening of the sky a little over the location of the setting or rising of the Sun on the horizon. In the northern hemisphere it can only be seen in the morning sky in autumn and in the evening sky in spring, while in the tropics it is visible all the year round as an almost triangular bright area.
Interplanetary gas originates mainly from the solar wind, which is a current of particles streaming out of the Sun's corona. A small portion consists of gases that have escaped from planetary atmospheres or the tails of comets. It is made up mainly of protons and electrons (electrically charged particles), but also has a helium component.
Initial information regarding interplanetary matter was found through observation of the zodiacal and corona light. Today there are space_probes gathering matter in order to analyze it in greater detail. As well as increasing our knowledge in general, the possibility of collisions between space stations or space vehicles is being examined. Calculations show that an area of 1 square meter would be hit only once every 30 million years by a particle with a mass of 1 gram.
