Sunday, 5 July 2009

Ask the Astronomer

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How many meteors enter the Earth's atmosphere every day?


In a recent article in the journal Nature, March 28, 1996 vol. 380, page 323, Dr.s A.D. Taylor, W. J. Baggaley and D. I. Street at the University of Adelaide in Australia discuss the results of their 1 year radar monitoring of incoming meteors. When meteorites slam into the atmosphere, they produce ionization in the atmosphere. Radar echos from this momentary ionization allow the velocity, altitude and distance to be determined if you have two or more such installations for triangulation. The AMOR radar in New Zealand was used for a year in this fashion to detect 350,000 faint echos from very small meteorites with sizes between 10 - 100 microns. This works out to nearly 1000 every day, just from this site alone! Over 1508 of these meteorites ( 0.9 percent) were found to be traveling at speeds up to several hundred kilometers per second!

On any given day, the estimates are than the Earth intercepts about 19,000 meteorites weighing over 3.5 ounces, every year of which fewer than 10 are ever recovered. About 2800 meteorites are in museums from previous 'falls' and are chemically found to represent about 20 or so distinct parent-bodies. The Earth acquires about 100 tons per day of dust-sized micro- meteoroids.

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