Asteroids 101

Asteroid Lutetia at closest approach.

Asteroids are small rocky objects that orbit the sun. They are leftover debris from the formation of the planets in our solar system. As such, they contain many of the same resources that we find on Earth. There are just shy of a million known asteroids, and 150 have been seen to even have their own tiny moons! They range in size from the size of a pebble to several hundred km across. Most of them are located in the asteroid belt, but there are groups of asteroids all over our solar system.

The four largest asteroids: 1 Ceres, 4 Vesta, 2 Pallas and 10 Hygiea

Because asteroids are leftover building blocks from the very early days of the solar system, they are very attractive targets for commercial and industrial purposes. They contain many of the same metal and mineral resources that we find on Earth. Asteroids are full of resources such as silver, gold, platinum, nickel, aluminum, iron, cobalt, and many more. 

In addition to resources, there are also asteroids and comets that have water and ice on them. Water is critical to any space exploration mission as it’s needed for life support, growing food, and rocket fuel.

Location Location Location

While there are many asteroids in our solar system, they are spread out all over. Most of them are in the main asteroid belt, but scientists have detected asteroids as far out as the Oort Cloud.

  • Main Belt The majority of known asteroids are within the Main Belt. It is located between Mars and Jupiter. It’s estimated that there are over 2 million asteroids over 1 km in diameter in the Belt. 
  • Jovian Orbit There are several groups of asteroids that are in the same orbit as Jupiter. They are clustered in three different groups, the Trojans, Greeks, and Hildas
  • Near-Earth Asteroids (NEA) – These are asteroids that have an orbit that bring them close to Earth. There are over 10,000 known NEAs that are over 1 km in diameter. The NEA are mostly liking to be the first locations chosen for surveying and eventually mining missions.
The inner Solar System, from the Sun to Jupiter.

Not every rock is the same

Asteroids are split into three main categories based on their composition. 

  • C-type asteroids are the most common, forming around 75% of all known asteroids. They are very dark due to a large amount of carbon in them. They contain large amounts of clay and silicate rock, and some of them could be as much as 22% water. 
  • S-type asteroids have much less water than C-type and are made up primarily of stony material and metals. These are very attractive mining targets as they contain resources like nickel, cobalt, gold, platinum and rhodium. 
  • M-type asteroids are not as common but contain up to 10 times more metal than S-types.

While metallic asteroids make up a small portion of the total number of asteroids, there are a lot of them out there! The largest M-type asteroid is 16 Psyche and it’s nearly 200km in diameter. Scientists believe that it’s an exposed iron core of a planet that was never formed.

The resources that are scarce on Earth are in abundance in space. There is everything we need to build a space faring civilization in space, waiting for us to use them.

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