The Asteroid Belt
Asteroids can be found throughout the solar system, but the majority of them are found in a region located between the planet Mars and Jupiter called the asteroid belt. Asteroids are basically chunks of rock and metal varying in size and shape. The size of each asteroid can be from a pebble to a few feet to hundreds of miles in diameter, and most are potato-shaped. Though they orbit the Sun between the rocky planets and gas planets, the asteroids do not rotate like a planet, but tumble and spin.
There are some asteroids which orbit near Earth and others which are sent further out into the solar system. There are literally millions and millions of asteroids orbiting the Sun at any given moment, and astronomers have individually identified about 7,000 of them. Each of them are identified by a number and by a name suggested by the discoverer.
Four of the largest asteroids identified by astronomers are Ceres, Vesta, Pallas, and Hygeia. These four asteroids take up half the mass of the entire asteroid belt, with the rest being much smaller. Ceres is the largest at about 590 miles in diameter, and is also designated as a dwarf planet. Its name comes from the Roman goddess of the harvest. Vesta is the next largest and is considered a minor planet at 326 miles in diameter. It is the brightest of the asteroids named after the Roman goddess of the home. Pallas was discovered after Ceres and is named after the Greek goddess Pallas Athena. Finally, Hygiea is the largest carbon-type asteroid named after the Greek goddess of health.
At one time, some astronomers had a theory that if all of the asteroids were combined, it would have made up another rocky planet adding it to the eight other planets. If joined together today, the mass of the entire asteroid belt would make up a planet smaller than the size of the Earth's moon.
Often, the asteroid belt is shown as a circle of different sized rocks orbiting the Sun, which is true, but they are far apart from each other. A person standing on one asteroid would not be able to see the closest asteroid with the naked eye, but would need a telescope. The large spaces between the asteroids has allowed spacecraft to travel through the belt without any collisions.
The three main types of asteroids are carbon, stony, and metallic. Carbon asteroids are made up mostly of rocks rich in an element called carbon and are very dark in color. About 75% of the asteroid belt is of this type. Stony asteroids are made up of some metal but are mostly rock. Metallic is the opposite of stony, and is made up of mostly metals with a small amount of stone mixed in with it.
Because of the minerals and metals in the asteroids, including nickel, iron, and titanium, they could ultimately be mined by humans. Most of the asteroids also contain water, which could help future space explorations if astronauts were ever sent to set up colonies for humans in space. The water would help keep the inhabitants in these colonies alive, and the minerals and metals could serve as materials to create the habitats where food can be grown. The main obstacle though to mining and creating space colonies is the affordable technology allowing humans to travel to the asteroids.
Astronomers refer to the large asteroid belt as the 'Main Belt' to distinguish it from smaller groups of asteroids called the Lagrangians and Centaurs, minor planets with unstable orbits, which can be found in other parts of the solar system.
In closing, the asteroid belt contains millions of individual asteroids made up of metal and rock located between Mars and Jupiter of the solar system.