Rocky Visitors, Part 2: Asteroids

Welcome to Part 2 of the Rocky Visitors series, where we’re exploring the fascinating, eerie, and sometimes dangerous rocky objects that live in the Solar System and visit Earth. In this article, we’ll be looking more in detail at asteroids.

Where asteroids live

Asteroids are space rocks that hang out in the Asteroid Belt, a region between Mars and Jupiter. Well, most of them do – you’d be able to find around 75% of asteroids in the Asteroid Belt. The other 25% are in the inner solar system (between the Sun and Mars) or further out in the Trojans, Greeks, or Hildas regions. In our solar system, there are millions of asteroids, many around half a mile wide! But don’t let the movies fool you – in reality, asteroids in the Asteroid Belt and other areas are spaced hundreds of thousands of miles apart! So, if you ever visited, you wouldn’t have to worry about your spaceship being crashed into.

Different types of asteroids

Because there are so many asteroids in our solar system, we’ve been able to place them into three different categories, or types, based on how they look. The three types of asteroids are C type, S type, and M type.

C type asteroids are the darkest asteroids you’ll find – they’re made up of mostly carbon and other minerals (carbon is the black stuff that’s left behind after a campfire). In fact, the “C” in C type comes from the “C” in carbon.  Around 75% of asteroids in our solar system are C types.

Carbon is the sooty, black stuff left behind after a campfire. On the right is a C type asteroid, called 253 Mathilde.

Asteroids can also be S types, which stands for stony or silicate types. This is because they’re made up of iron and silicate (silicate is just silicon with some extra chemicals added to it). They also don’t have as much carbon as the C types. This means that S type asteroids are lighter and more reflective.  Around 17 % of asteroids are S types.

Lastly are the rarest group of asteroids, called M types. They make up around 8% of asteroids and are the brightest in our solar system. The M in their name stands for metallic, which means they’re made up of mostly metallic, shiny iron. What’s amazing is that one M type asteroid, about a half-mile wide, could supply the Earth with enough iron for a very, very long time!

Awesome asteroids

While all asteroids are very cool, there are some that are so odd and fascinating that they just blow us away. Here are some of those weird and amazing asteroids.

16 Psyche

Remember the M types? The shiny, metallic asteroids with a lot of iron? Well, 16 Psyche is one of them, and it’s truly mind-blowing. This 140 mile wide M type asteroid is made up of so much iron and nickel that it would cost more than our world’s entire economy! That’s quadrillions of dollars! We know it has all this metal because it’s one of the brightest asteroids in the solar system. What’s exciting is that next August, NASA plans to send a spacecraft to visit and study 16 Psyche.  So, stay tuned!

This is a drawing of 16 Psyche.

Vesta

Vesta is the second largest asteroid in our solar system, with a diameter of around 326 miles. It’s also known as 4 Vesta because it was the fourth asteroid ever discovered – a German astronomer found it in 1807. But the reason why Vesta is so cool is that it might have had volcanos on it long ago! We think this because Vesta is differentiated, meaning, it has a crust like Earth, a mantle on top of molten lava, and a core in its center. Vesta isn’t volcanically active now (meaning, its volcanos don’t spew out lava), but there’s evidence that this happened billions of years ago. So, you can think of Vesta as a mini planet! In fact, astronomers call Vesta a protoplanet, because it's very similar to a planet, but not quite big enough.

This is a photo of Vesta, taken by the Hubble Telescope. The round spot in the middle is a mountain called Rheasilvia, and it’s the tallest mountain in the entire solar system! Rheasilvia is 14 miles tall!

Well, that’s all for our tour of the asteroids in our solar system. In the next part of the Rocky Visitors series, we’ll be looking at comets!