Jason King, age 12, of Poughkeepsie, N.Y. , for his question:
WHAT IS THE DIFFERENCE BETWEEN A METEOR AND A METEORITE?
In astronomy, a meteor is a small solid body of matter that enters the earth's atmosphere from outer space and it burns up because of the friction resulting from its rapid motion. A meteorite, on the other hand, is a meteor that actually reaches the earth's surface before it is completely consumed.
Friction makes the meteor glow brightly with heat as it flashes through the atmosphere. Brilliant meteors, known as fireballs, occur singly and generally consist of a luminous head, followed by a cometlike train of light that may persist for a number of seconds.
Some meteors, called bolides, have been seen to explode with a sound like thunder. Fainter meteors, called shooting or falling stars, usually occur singly and sporadically. At times, however, hundreds of such meteors occur at the same time and appear to emanate from a fixed position. These swarms are called meteoric showers.
A meteor that reaches the earth's surface is called a meteorite. Meteorites are classified into three types, according to their composition: siderites, those composed chiefly of iron, a small percentage of nickel and traces of other metals such as cobalt; aerotites, stony meteors consisting of silicates; and siderolites, containing varying proportions of both iron and stone.
Because no unfamiliar substance has been found in meteorites, they are believed to fragments of a body resembling the earth, some representing the core and others originating from the crust. Meteorites generally have a pitted surface and fused charred crust. The larger ones strike the earth with tremendous impact, creating huge craters.
The largest known meteorite, estimated to weigh about 55 tons, is situated at Hoba West near Grootfontein, Namibia, southwest Africa. The next largest, weighing more than 31 tons, was discovered, along with two smaller meteorites, in 1894 near Cape York, Greenland.
The American explorer Robert Peary discovered the 31‑ton meteorite found in Greenland. Composed chiefly of iron, the three masses had long been used by the Inuit (Eskimo) as a source of metal for the manufacture of knives and other weapons. The large meteorite was named Ahnighito, or the Tent.
The Ahnighito was brought to the United States by Peary and is now on display at the Hayden Planetarium in New York City.
The largest known crater believed to have been produced by a meteorite was discovered in 1950 in northwestern Quebec, Canada. It consists of a circular pit 2.5 miles in diameter, containing a lake and surrounded by concentric piles of shattered granite.
The age of meteorites has been estimated at about 5 billion years, indicating that meteorites originated at about the same time as the earth.
Most meteors are dissipated in flight and fall to the earth as nothing more than dust.