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Characteristics of Asteroids Vs. Meteorites

The terms asteroid and meteorite are often used interchangeably. The popular conception is that rocks in space are all the same thing. In fact, asteroids and meteors are very different objects. Scientists have studied both of these space rocks for many years, but deep mysteries still remain. Monitoring the paths of these rocks as they hurtle through space is crucial in predicting close encounters.

Solar System History
- Both asteroid and meteors likely formed about the same time as everything else in the Solar System about 4.5 billion years ago. The early Solar System was a mixture of young planets and rocky debris. Collisions between objects were frequent and violent. Some material settled into stable orbits, while the rest was jettisoned to the Solar System's outer reaches. After the initial chaos, the Solar System, including asteroids and meteors, entered a period of relative stability.
Asteroids
- A few asteroids have been visited by spacecraft.
  
  Asteroids are rocky, metallic bodies that can be several hundred miles across, though most are quite small. The largest asteroid, Ceres, has enough mass for gravity to force it into a spherical shape. The vast majority of these rocks are oddly shaped. All the asteroids in the Solar System put together would not equal the mass of the moon, and yet they have been critical in the history of life on Earth. Scientists theorize that an asteroid impact wiped out the dinosaurs 65 million years ago.
Meteorites
- A meteorite is a rocky body that has fallen to the Earth's surface. Their origins are less clear than asteroids. While falling, it's called a meteor and creates a bright streak in the sky. Some meteors are the size of dust grains and vaporize in the air. Meteorites sometimes resemble Earth rocks. They can be dense and metallic or rocky. Meteors are falling through the atmosphere all the time. According to NASA scientists, more than 1,000 tons of meteorites land on Earth each day.
Dangers
- Large craters on the moon demonstrate the power of impacts.
  
  The processes of weathering and erosion are constantly active on Earth. This covers up most evidence of asteroid and meteor impacts much more quickly than on a dead surface like the moon. Many people don't realize that the Earth has been bombarded countless times, and will be again. Scientists agree that an asteroid impact likely exterminated the dinosaurs, so the need to keep a watchful eye on objects orbiting near the Earth is clear.

Astronomy