Before starting, let’s recap the differences between asteroids, meteors, and comets:
ASTEROIDS VS COMETS: Asteroids formed closer to the sun because they don’t have ice. This differentiates them from comets which are just balls of frozen ice, water and rocks.
ASTEROIDS VS METEORS: Asteroids are larger in size than meteors spanning more than one meter in diameter. In general, meteors have a diameter of one meter or less.
Now, we know how they’re different. Let’s dig a bit deeper with these rocky and metal objects. Here are 3 facts about asteroids.
1. The asteroid belt is between Jupiter and Mars
Think of the asteroids as being smack dab in the middle of a gravity tug-of-war. Neither side is winning so asteroids are stuck in between.
The asteroid belt is kilometers in size. If you were to take all the asteroids and put them together, they would make up just 4% of the mass of the moon.
This means that there’s really not a lot of material in the asteroid belt orbiting the sun. The largest asteroid is Ceres and is considered a dwarf planet because of its size.
2. Asteroids didn’t mould into planets
The most common way of thinking is that asteroids are remnants of the early solar system. During the creation of our solar system, dust coalesced to form planets like Earth.
Asteroids were loose chunks of metal and rock. When they were large enough in size, gravity would start taking over. But the smaller ones never formed a planet.
In the early solar system, more and more debris would form baby planetesimals. Then, there were millions of planetesimals whizzing around the solar system. Some collided and grew larger. But asteroids and planetesimals were never allowed to become a planet because they never had the opportunity to do so.
3. About 30 asteroids strike Earth each year
Some asteroids that crash into Earth are larger than others. We know that about 30 asteroids hit the Earth per year because NASA tracks them with their bolide events map.
We monitor asteroids because they swing into Earth’s orbit causing changes on Earth. There is evidence of large asteroid collision events in Earth’s history such as in the Cenozoic Era.
For example, there is evidence that an asteroid or comet crashed into the Gulf of Mexico. This impact was first revealed from the Chicxulub crater which ultimately triggered the extinction of the dinosaurs 65 million years ago. Also, in Siberia, the Tunguska event is the largest recorded impact in history. This impact was either caused by an asteroid or comet.
Size comparison between asteroids and our moon
Here is a relative size comparison between some of the well-known asteroids in our solar system compared to the moon.
1. Dwarf planet Ceres