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Meteoroid: Definition & Facts

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

After completing this lesson, you will be able to explain what a meteoroid is, what they're made of, and how big they are. You'll be able to distinguish between the types of meteoroid, and know the difference between asteroids, meteoroids, meteors and meteorites. A short quiz will follow.

What is a Meteoroid?

A Meteoroid
A Meteoroid

A meteoroid is a small rocky or metallic object travelling through space. While most things are named for what they are, rocks in space are named partly for where they are. A small rocky or metallic object burning up in Earth's atmosphere is called a meteor. And a small rocky or metallic object that has already hit the Earth's surface is called a meteorite.

A Meteor in Earths Atmosphere
A Meteor in Earths Atmosphere

Where do meteoroids come from? Well, they can come from a lot of places. But most often they're bits of rock that have broken off from larger asteroids or comets in the solar system. Sometimes they can also be the result of collisions with planets. If a large asteroid hits the Earth, bits of the Earth's surface can be broken off and sent into space, for example.

A Meteorite in a Lab
A Meteorite in a Lab

Types of Meteoroid

There are three types of meteoroid, based on what they're made out of. Most meteoroids contain nickel and iron. But how much of them is made of these metals varies.

Meteoroids that are mostly made out of iron are called irons. Meteoroids that are mostly made out of rock are called stones. And meteoroids that are a fairly even mix are called stony irons.

Meteoroid Facts

Here are some facts about meteoroids:

• When a meteoroid burns up in the atmosphere as a meteor, its color is affected by what materials make it up and how fast it's moving. They can burn with an orange, yellow, blue, green, or even violet tint.

• Whenever a meteoroid hits a planet or moon, it creates a crater. These craters get eroded away on the Earth and other active bodies, because of volcanic activity and weather. But on less geologically active bodies like the Moon, they stay around a lot longer. This is why there are so many craters on the Moon.

• If a meteoroid is larger than 1 meters, it's usually considered to be an asteroid. If it's smaller than grain-size, it's usually called space dust or a micrometeoroid.

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