Facts about Meteorites and Asteroids

Asteroids are similar to planets, but they are much smaller and can be irregular in shape.  Most of them are between Mars and Jupiter, but some come so close to the Earth that they are watched in case an impact happens. Icarus is one of the biggest asteroids that comes close to the Earth. Meteorites are meteors that have hit the Earth and made an impact if they are big enough. Meteors, also called shooting stars, are the remains of comets that orbited the Sun and were broken up.  

Icarus was discovered in 1949 by Walter Baade. It was named 1566 Icarus. It is classified in the near-Earth asteroid group Apollo asteroids. Its path comes closer to the Sun than Mercury. Icarus makes periodic close approaches to the Earth every 9, 19, and 38 years. On June 14, 1968 it made a very close approach when it came within 4 million miles of the Earth. On June 16, 2015 it will be within 5 million miles of the Earth.  The data is just approximate, but the odds of an impact are slim.    

According to dictionary.com, a meteorite is “A mass of stone or metal that has reached the earth from outer space; a fallen meteoroid.” It defines an asteroid as “… Astronomy . Any of the thousands of small bodies of from 480 miles (775 km) to less than one mile (1.6 km) in diameter that revolve about the sun in orbits lying mostly between those of Mars and Jupiter.”

Comet, asteroid, meteoroid, meteor, and meteorite are terms that have similar meanings. A comet is composed of dirt and ices. They have beautiful dust and gas tails. Comets orbit the sun periodically. An asteroid is a large object that is similar to but smaller than a planet. It is composed of rock, metal, or carbon. A meteoroid is part of an asteroid that has blown off or part of a comet that has broken up. A meteor is a meteoroid that has hit the Earth’s atmosphere and disintegrated. If a meteor is big enough to hit the Earth, it is called a meteorite.    

Asteroids are sometimes called minor planets because they are similar to planets but smaller. One big difference between asteroids and planets is planets have atmospheres but asteroids do not.

Five per cent of the meteorites on the Earth were probably once part of the third to the largest asteroid Vesta. Meteorites formed in a variety of ways. Meteorites that have formed in igneous processes similar to the processes on Earth are hard to identify as meteorites because they look similar. The achondrites  But others were formed different from the igneous processes found on Earth, which makes it easier to identify them. Other types of meteorites are primitive chondrites, equilibrated chondrites, iron meteorites, and pallasites.

Primitive chondrites have a dark gray crust and interior. Three basic components that might be visible on broken surfaces are chondrules, matrices, and refractory inclusions. Equilibrated meteorites are mostly composed of olivine, pyroxene, and feldspar, but usually contain a small amount of metal. Iron Meteorites are very dense and nonporous. Pallasites are mixtures of metal and silicate materials.