Asteroids

Asteroids, small solar system bodies composed of rock and metal, are left over from the early days of the Solar System. Most asteroids orbit around the Sun in a belt between Mars and Jupiter and travel in the same direction as the planets.

(Image Right: Asteroids, Courtesy of NASA)

Features

: Features of the asteroid Vesta (B. Zellner / Georgia Southern University, NASA)

Astronomers believe that there are three types of asteroids - those made of rock, those made of metal, and those that are a mixture of the two. Asteroids are remnants from the giant cloud of dust and gas that formed the Solar System some 4.6 billion years ago.

Most scientists believe that the strong gravitational forces of Jupiter prevented these clumps of rock from sticking together to form another planet.

The term asteroid comes from an ancient Greek word meaning "star-like." Most asteroids are shaped irregularly - like potatoes. They are often covered with craters, fractures, and dust from collisions with other objects in space.

Many asteroids are composed of silicates (stone), metals, (iron and nickel), or a combination of those materials. Some also contain carbon-rich substances. Although asteroids are not planets, they can have moons.

Discover more about asteroids at NASA's Solar System Exploration website.

Missions

: DAWN Spacecraft (Background- William K. Hartmann, Courtesy of UCLA; image-NASA/MCREL)

Asteroids are so far apart you could fly through the asteroid belt and never see a single one from your spaceship window. First observed with telescopes in the early 1800s, asteroids continue to be studied by scientists.

In October 1991, NASA's Galileo spacecraft visited Gaspra, the first asteroid to be observed close up. The Near-Earth Asteroid Rendezvous (NEAR) mission to Eros was the first to land a spacecraft on an asteroid's surface in 2001. Today you can follow the Dawn mission as it heads to Ceres and Vesta.

Learn more about missions to asteroids at NASA's Solar System Exploration page.

Myths, Stories, and More

: Asteroid (43844) Rowling discovered by Adler astronomer, Mark Hammergren. (Image taken from applet provided by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL).)

The first asteroids were named after figures from Greek and Roman mythology such as Ceres and Vesta after the Roman goddesses of agriculture and of the hearth. . Asteroids that orbit the Sun on the same path as Jupiter are named after figures from the Trojan war such as Archilles, Agamemnon, and Odysseus.

Other asteroids are named after writers like Shakespeare and Tolkein, Others are even named after musicians like the Beatles and Enya.

Find out more about naming an Asteroid at Space.com

Earth Matters

: Vesta, Ceres, the Moon, Earth (Original Image NASA)

Scientists are especially interested in asteroids because they likely are leftovers from the formation of the Solar System. Asteroids should provide clues to the material that gave birth to Earth and the other planets. Stray asteroids likely slammed into the Earth, playing an important role in the geological history of our planet as well as the evolution of life.

Find out more about asteroids and Earth at SolStation.com.