Space mining refers to the hypothetical process of retrieving minerals from near Earth objects such as asteroids and comets. Some scientists believe that space mining could help address human population growth and increasing demand for resources.

Asteroids are rich in the raw materials required to build structures, while comets are replete with water and carbon. They also contain large amounts of liquid hydrogen and oxygen, which are used in rocket fuel.

According to NASA, the asteroids between the orbits of Mars and Jupiter may contain the equivalent of about 100 billion dollars for every person alive today. While it is not currently cost effective to bring the materials back to earth, they could be used to build structures and create refueling stations in space. Space mining could eliminate the need to launch large structures from Earth, dramatically reducing the cost of exploring and colonizing space.

A 2013 NASA report that explored the feasibility of space mining suggested that humans would only need to launch 12 tons of lightweight electronics, wiring, machines, and 3D printers to create a robotic manufacturing base in Earth’s orbit. The robots would start by creating solar cells that would power the system. The first generation of robots would extract and refine raw materials, then fashion and assemble the parts required to create the next generation. The robots could add improvements to subsequent models to advance the system’s mining and manufacturing capabilities.

It would only take six generations for such an enterprise to become a self-sustaining system in which robots would be able to construct and run themselves without materials from Earth, according to the report. As the system matures and begins extracting more materials than are required for use in space, it may eventually become possible to send them down to Earth.

NASA has announced plans for a future Asteroid Redirect Mission (ARM) in which it would capture a small boulder from a near Earth asteroid and move it into orbit around the moon, where astronauts can visit it to collect rock samples. While the agency is currently using asteroid (341843) 2008 EV5 for planning purposes, it will announce the final target in 2019.