Meteor dust
As meteor dust of fine precipitate is called, which the burning up of shooting stars and larger meteors created and trickles slowly to the ground. These particles are smaller than 0.1 mm.
But micrometeorites also contribute to this aerosol if they are too small to burn up with a diameter of less than 1 mm. When they penetrate into the high atmosphere, because the mass-to-cross-section ratio is too low, they are slowed down so quickly that no strong heating occurs and they sink without significant melting processes.
The amount of meteoritic dust outweighs the mass of the larger particles falling to the ground, the meteorites , by several orders of magnitude. The estimates for the entire surface of the earth are between a few hundred and about 5000 tons per day.
Large meteorite impacts in the early history of the earth can often only be detected by the dust-like precipitation that is found in the rock layers that were then sedimented . This dust can e.g. B. contain the platinum metal iridium in a far higher proportion than the normal earth's crust . Therefore, an extraterrestrial origin can be assumed for a sediment with a high concentration of iridium.
See also
literature
- Otto Struve et al .: Astronomy. Introduction to their basics , Chapter 14.5 "Micrometeorites". De Gruyter, Berlin 1967
- Arnold Hanslmeier: Introduction to Astronomy and Astrophysics , Chapter 6.14 " Meteoroids ". Springer Spektrum Verlag, Berlin 2013