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Asteroid Facts

There are a lot of different objects in outer space. Some are pretty easy to spot, like the Moon! But there are celestial objects that are so far away that your naked eye can’t see them. You would need a telescope or a satellite armed with a camera. One of these things are asteroids!

A 3D illustration of asteroids in space.

You might think that the night sky is pretty full. But you are definitely not seeing all of the things in the universe – like asteroids!

What are Asteroids? 

Think about asteroids as space rocks that orbit the Sun! Asteroids are the space ingredients that didn’t make it into full-fledged planets. Because of this, very few asteroids look like spheres. In fact, they rarely fit any regular shape descriptions! Asteroids are also very different in size. Some are hundreds of miles wide, and some are only measured in feet! The smallest asteroid ever found is the 6-foot-wide 2015 TC25 rock! 


There is no fixed picture of what an asteroid should look like. That’s because asteroids come in all shapes and sizes!

Asteroids all have different mixtures of rock and metals! Scientists separate asteroids into categories, or spectral classes – kind of like stars! These special classes are based mainly on two things. The asteroid’s composition, and the way they reflect light! Here are the three most common asteroid categories:
  • C-type, or carbonaceous asteroids. These have lots of carbon and other organic compounds. They also contain a good deal of iron. They’re gray-ish in color, and are the most common type of asteroids out there! 
  • S-type, or silicaceous asteroids. They’re made up of silicate materials. These asteroids tend have a red color, and are sometimes referred to as stony asteroids! S-type for stony works too, right? 
  • M-type, or metallic asteroids. These are exactly what their name suggests – mostly metals! They’re made up of iron and nickel, and look a little reddish! 

    A 3D illustration of metallic asteroids.

    Fun fact: scientists have discovered that asteroids are rich in rare metals. Get ready to welcome a new type of mining – asteroid mining!

Where Do Asteroids Come From?

Asteroids come mostly from the Asteroid Belt. This belt takes up the area between Mars and Jupiter. The Asteroid Belt is not just a small strip with a dense asteroid population! Asteroids in the Asteroid Belt are actually pretty far from each other. The average distance between 2 asteroids is around 600,000 miles – more than the distance from Earth to the Moon! Still, many asteroids lie outside of the main belt. Around 17,000 asteroids actually cross pretty close to the Earth! 
You can divide the Asteroid Belt into an inner and outer belt. The inner belt is within 250 million miles of the Sun! It consists mostly of metallic asteroids. The outer belt lies beyond the 250 million mile boundary. It is made up of more stony, carbon-based asteroids. 

An illustration of the Solar System, showing the asteroid belt.

The asteroid belt may seem small on a diagram, but don’t let the scale fool you! 

How One Asteroid Wiped Out the Dinosaurs

Long, long ago, dinosaurs roamed our planet. But now, we only have dinosaurs in museums and science fiction films! So what happened to kill out such a mighty race? Well, one theory is that an asteroid was responsible for the extinction of dinosaurs – 65 million years ago!
Scientists think that the Chicxulub Crater in Mexico is where the asteroid hit the Earth! The crater is a whopping 93 miles in diameter, but the asteroid was probably only 6 or 9 miles wide! For its size, the asteroid sure did a lot of damage! 
A 3D illustration of an asteroid impacting with the Earth.

How could a seemingly small asteroid have such a disastrous impact? You have to account for its speed as well! It was probably traveling at around 10 miles per SECOND

If this got you scared of asteroids colliding with the Earth, don’t worry! The chances of an asteroid hitting Earth are really very low. Besides, the National Aeronautics and Space Administration’s – or NASA’s – technology will keep us safe! They can predict if a collision might happen way in advance, and have plans to slowly change the asteroid’s course

Asteroids, Comets, or Meteors?

As you learned before, there are lots of things in the universe other than asteroids. Asteroids are often confused with comets and meteoroids. These three may look the same, but they’re really not!
Let’s start with asteroids and comets. Asteroids and comets are both large, floating space objects. But unlike asteroids, comets are icy – not rocky.
So what about meteoroids? Well, meteoroids and asteroids are both rocky. The big difference lies in their size: meteoroids are much smaller than asteroids! And when they fall to Earth they’re called meteors. Lots of meteors fall down to Earth, but they aren’t nearly as dangerous as asteroids! 

A 3D illustration of a meteor shower.

Many people go to watch meteor showers. But if there was an asteroid shower, Earth would be in full panic mode!

Other Great Resources


Asteroid Formation: https://www.space.com/51-asteroids-formation-discovery-and-exploration.html

More Facts About Asteroids: https://www.timeanddate.com/astronomy/asteroid.html

Asteroids Vs. Meteors: https://spaceplace.nasa.gov/asteroid-or-meteor/en/



Crash Course on Asteroids: https://www.youtube.com/watch?v=auxpcdQimCs

What is an Asteroid?https://www.youtube.com/watch?v=iy19nHTVLEY

How Asteroids Killed the Dinosaurs: https://www.youtube.com/watch?v=kpLY0YwMACE


Written by: Minh Nguyen