The Space & Beyond Blog
What aRE asteroidS?
The different types of asteroids and where they are located
Asteroids are chunks of rock and metal that orbit the Sun. They can be different shapes and sizes and they sometimes collide with the Earth. Sometimes they are as small as the size of a pebble; however, the largest known asteroid is Ceres, which is around 597 miles (960 kilometers) in diameter.
This color picture is made by the imaging system on NASA’s Galileo spacecraft before its closest approach to asteroid 243 Ida. The range from the spacecraft was about 10,500 kilometers (6,500 miles). Ida’s moon (Dactyl) is visible to the right of the asteroid. Photo: NASA/JPL
The three broad composition classes
There are three major types of asteroids: C-Carbonaceous (comprised of ancient carbon silicates), S-Silicates (made of rocky silicates and iron), and M-Types (rich in metals, mostly nickel and iron).
Where are asteroids found
The largest population of asteroids lies between the orbits of Mars and Jupiter in the asteroid belt. However, a significant number are found within the orbits of Mars, Earth, Venus, and Mercury. Less than 200 asteroids orbit close enough to Earth to be considered a threat. These bodies are known as near-Earth objects.
There are over 10,000 identified bodies in the asteroid belt that are between 60 miles (100 km) and 600 miles (1,000 km) across.