Overview of the Sizes and Frequencies of Meteors and Meteorites Hitting the Earths Atmosphere

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"Overview of the Sizes and Frequencies of Meteors and Meteorites Hitting the Earths Atmosphere"
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The rate of meteors by weight, coming in contact with with the Earth's atmosphere is termed meteor flux. The smallest particles, called micrometeorites, are a few microns in diameter and don't tend to burn or melt but slow and settle to the Earth's surface as dust. Meteors of a few centimeters or less tend to heat up and glow and appear as shooting stars but melt or evaporate before hitting the Earth's surface. Meteors of greater than a few centimeters are called meteoroids until impacting the Earth when they are termed meteorites.

The total mass per year accumulating on the Earth is estimated between 10 million and 1 billion kilograms per year (11,000 to 1,000,000 tons). Common measuring systems are either optical, sensing the light emitted during atmospheric entry, or radar echos. There have also been calculations of meteor flux based on finds of meteorites in the Antarctic. Converting the optical or radar information to weight is where the great variance in estimates originate. This article details some current research on the subject of radar power and meteor flux mass calculations. The Leibniz Institute offers a good deal of information on meteor flux and a real time counter of radar detected meteor flux. The daily rate can vary depending on the position of the Earth in relation to other celestial events such as debris left in the wake of comets. Comet trails result in meteor showers which are dramatic increases of meteor flux.

Most of the mass of meteor flux is micrometeorites. Objects of 1 micron land on the Earth at a rate of over 2 million per minute. Meteorites of 1 mm reach the surface at about 2 per minute. An object of 1 meter in diameter impacts with the Earth about once a year. Larger meteorites, such as the Tunguska event in 1908 estimated at 20-60 meters in diameter, or Meteor Crater in Arizona estimated at 30 meters, occur about once in 5,000 to 10,000 years.

Catastrophic impacts of 1 kilometer diameter can occur about once in a million years. And a 10 kilometer object could impact every 100 million years. These are climate changing, mass extinction events like the Chicxulub impact event of 65 million years ago thought to be responsible for the extinction of the dinosaurs.

A currently accepted theory allows for a planet size collision about 4.5 billion years ago that resulted in complete destruction of the surface of the Earth and ejected enough debris into Earth orbit to create Earth's Moon.  

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