Asteroid mining offers the possibility of a nearly inexhaustible supply of minerals, ranging from base metals such as nickel and iron to valuable ores like gold, silver and iridium. Asteroids may also allow long-term space missions or colonies to find their own resources instead of relying on materials brought up from Earth. However, until spaceflight becomes much cheaper, asteroid mining remains firmly in the realm of scientific curiosity.
Much of the mineral wealth in the Earth's crust comes from asteroids. Early in the planet's development, gravity drew most of the heavier elements in the protoplanet's structure into the core, leaving a crust made of silicates and lighter elements. Asteroid bombardments early in the planet's lifespan seeded the crust with mineral deposits, however, and much of the minerals used by humanity today come from these extraterrestrial impacts. The same minerals, in much greater quantities, can be found throughout the asteroid belt.
In 2012, the company Planetary Resources announced its intention to mine an asteroid, and a number of competitors followed suit shortly afterward. Miners are drawn by the lure of incredible riches, as a single asteroid could hold more platinum or iridium than exists in all known deposits on Earth. In the future, if the cost of spaceflight decreases, and as resources on Earth become more scarce, the asteroid belt will become a much more tempting target for exploration and exploitation.