What Are Asteroids Made Of?

An asteroid is a large chunk of matter made up of rock and/or metal that is either found within the Asteroid Belt between Mars and Jupiter or orbiting the solar system. They can range in size from the size of a particle of dust to many miles across; therefore, there are many different ways to classify an asteroid. However, when it comes to what their made of, there are only three ways to classify them and group them together.

The first way which is the first material that they're made of is called rock. When an asteroid–or a meteorite at the time–hits the ground, it is hard to tell that it is, in fact, from space because the rock looks so similar to the terrestrial rock. And because they weather much faster than the other types of asteroids, they quickly don't look like anything other than a simple rock on Earth. Most asteroids fall into this category–92.8% to be exact and they are made up of silicates.

The second kind of asteroid is one that is made up of metal. The mixture of metal is typical iron and nickle. Because they are made of metal, when one of these hits the Earth, they are more likely to be found and recorded as an asteroid because they don't appear like terrestrial rock. However, since only 5.7% of all the asteroids fall in this category, it's obvious that there's a smaller chance of finding one of these.

The final kind is a hybrid of both. These are asteroids that are made up of rock–specifically the silicates that make up the rock–and iron/nickle. They are usually found with a balance of the two materials. Doing the math, it's easy to see how few of these there are out there. With only 1.5% of all asteroids falling in this category, finding one of these is nearly impossible.

Where do Asteroids Come From?

One theory is that they were formed from a planet that was destroyed. However, because of the size of all the asteroids put together–only about 1,500 km–it's unlikely that this theory is probable. There's a good chance that there were very large asteroids that were bombarded with smaller ones which resulted in these large ones breaking apart into smaller ones. And as they continued to get hit, more smaller ones were made.