Many of us have seen meteor showers like the Leonids shown here in a NASA image seen at 38,000 feet from Leonid Multi Instrument Aircraft Campaign (Leonid MAC) with 50 mm camera. Credit: NASA/Ames Research Center/ISAS/Shinsuke Abe and Hajime Yano
In an 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 one- year radar monitoring of incoming meteors. When meteorites slam into the atmosphere, they produce ionization in the atmosphere. Radar echoes 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 echoes 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.
Every night, a network of NASA all-sky cameras scans the skies above the United States for meteoritic fireballs. Most meteors you see in the sky are causes by rice-grain-sized rocks that burn up rapidly through friction. But bolides are especially large. These are objects that can be as large as marbles or basketballs! Automated software maintained by NASA’s Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth’s atmosphere and many other characteristics. Daily results are presented at Spaceweather.com. Here is a map for a typical day’s worth of bolides. On February 27, 2017 there were 9 bolides detected by the network. Note all orbits intersect at the location of Earth…of course!
Here is a particularly busy day around the time of the 2016 Perseid Meteor Shower when 262 fireballs were recorded on August 12!
