by Andy Greenspon

Have you ever wondered how much gold remains to be mined on Earth? How about the lesser-known element indium, essential to computer and smartphone displays? Known sources of some metals could be depleted in as little as 20 to 30 years, especially the rarest ones necessary to construct computers, smartphones, and other advanced technologies. While some elements can be substituted for others, many metals are effectively irreplaceable because of their unique properties. While we may find new sources of these metals, it will likely be harder to extract them, leading to increased costs and a need for cheaper alternative sources. If we can’t find them on Earth, we’ll have to begin searching the rest of our solar system, starting with asteroids.

A Neighborhood of Asteroids

Asteroids formed billions of years ago in our inner solar system and are composed of rock, metals, and water. The asteroid belt between Mars and Jupiter contains millions of asteroids, ranging in size from as small as a pebble to a diameter 7.4% that of Earth. Scientists have also discovered around 15,000 near-Earth asteroids (NEAs) closer to home (Figure 1).

Figure 1: Previously discovered asteroids categorized by size (top-to-bottom) and number (left-to-right). Ceres, the largest single asteroid, is found at the top left hand corner of the graph. The smallest ateroids, of which there are more than 1 million, are located at the bottom right corner. Image by Marco Colombo, DensityDesign Research Lab, licensed under a CC BY-SA 4.0 license.
Figure 1: Previously discovered asteroids categorized by size (top-to-bottom) and number (left-to-right). Ceres, the largest single asteroid, is found at the top left hand corner of the graph. The smallest ateroids, of which there are more than 1 million, are located at the bottom right corner. Image by Marco Colombo, DensityDesign Research Lab, licensed under a CC BY-SA 4.0 license.

While scientists study asteroids to better understand the formation of the solar system and humanity’s origins on this rock we call home, asteroids could become economically valuable as well. Asteroids often contain important metals such as iron, nickel, and cobalt, as well as small amounts of precious metals such as platinum (Figure 2). Given these considerations, a single asteroid with the right composition could be worth trillions of dollars in raw materials.

Figure 2. The abundance of industrial metals in asteroid varieties compared to Earth’s crust. Meteorite composition data from
Figure 2: The abundance of industrial metals in asteroid varieties compared to Earth’s crust. Meteorite composition data from Figure by Mary Gearing.

Getting from Here to There

Let’s start from the beginning: How would we actually mine an asteroid? In the simplest terms, it would be similar to mining on Earth, but with the added complications of working in space. First, we’d need spacecraft that are able to carry the mining equipment from Earth to the asteroid. NASA is currently working on this first obstacle; OSIRIS-REx, just launched in September, will travel to the near-Earth asteroid Bennu to collect and return a small sample from its surface.

Beyond transit, the mining process itself poses a challenge. Keep in mind that asteroid mining would be primarily operated by remote controlled robots, and you can see the challenges of this endeavor. Typically, mined raw ores contain a mixture of compounds with a wide variety of metals. Those compounds must then be separated, often through complex chemical reactions, to retrieve the pure metals for use in applications. Companies could transport either the raw ores or the purified metals directly back to Earth, depending on the costs of processing the raw ores in space versus transporting the extra weight of raw material back to Earth.

Mined materials could also be processed in space or on a future space colony in order to directly construct structures for use in space. Since the cost of launching materials off of Earth is extremely expensive, delivering the raw or processed materials directly from an asteroid could save on rocket construction, fuel, and time needed to deliver resources. First, however, we need to develop techniques to process raw ores in the zero gravity environment of space, no easy task. In addition, all mining technology would have to be as light as possible to more easily move it around in space.

Has the Asteroid Space Race Begun?

Given all the complexities and obstacles described above, asteroid mining is not currently technologically or economically feasible. Asteroid mining will only become a reality if 1. mining for materials on asteroids becomes cheaper than mining them on Earth, or 2. mining and processing materials in space for use in space becomes cheaper than launching and sending spacecraft with those materials from Earth. Given humanity’s exponential increase in raw material consumption and entrepreneurs’ desires to push the limits of spaceflight, this scenario could become a reality sooner than we think.

Currently there are two known companies with a long-term focus on asteroid mining: Planetary Resources and Deep Space Industries (DSI), founded in 2010 and 2013, respectively. Planetary Resources raised $21 million this year to launch satellites with sensors to help manage natural resources on Earth. They plan to use this technology to eventually scan from afar near-Earth asteroids to identify desired materials. Within a decade, they and DSI hope to send survey probes to asteroids to map their surfaces and collect samples. Both companies hope to determine the best asteroids for mining of not just metals but also water ice that can be “converted into drinking water, breathable air, and rocket propellants” for use in a space economy. The ultimate goal is to use fully automated robotic systems for mining, processing, and transporting products wherever they are desired, whether on Earth or in space.

An Asteroid Mining Free for All?

If technology advances enough to make asteroid mining economically feasible, would it even be legal? Under whose authority would a mining company operate? The United Nations General Assembly first addressed the issue by establishing The Committee on the Peaceful Uses of Outer Space (COPUOS). This Committee helps establish international norms for governing the use of space for peaceful purposes and scientific advancement, and facilitated the creation of five treaties involving outer space.

The most important treaty for asteroid mining is the 1967 Outer Space Treaty, which establishes a legal framework for all activities in space. The Treaty forbids any government from claiming the Moon or any other celestial body under its own sovereignty. However, this does not explicitly prohibit a corporation or even a nation from mining or using resources from space for a profit. Nonetheless, the Treaty states that nations can “use” outer space but “for the benefit of mankind” and “that states shall avoid harmful contamination of space.” Both of these statements conflict with any private company or individual nation setting up a mining operation on any celestial body.

It is therefore unclear whether a corporation could actively mine an asteroid for its own profits. The position of the United States is that while a company or the U.S. cannot claim ownership of an area of a celestial body, once a company mines resources, those resources become the property of the miner. The U.S. further solidified this position by passing the Spurring Private Aerospace Competitiveness and Entrepreneurship (SPACE) Act of 2015, which included language allowing U.S. citizens to engage in commercial exploration, extraction, and sale of non-biological natural resources such as water and minerals from asteroids and other celestial bodies. As a result, any asteroid resources mined by American companies in space would be considered their property. Whether or not anyone will mount an international legal challenge to this part of the law remains to be seen.

The first company to successfully mine resources of any size will open a floodgate of legal issues that will have to be addressed. For example, even if mining is permitted by the nations of the world, what will an individual corporation have to do to claim an area for mining? Perform a scientific survey with a satellite from orbit? Place a lander on the surface? Establish a complete mining operation at the location? Would each company only have a claim on the resources it can mine off of a celestial body? These are difficult questions. Even the SPACE Act of 2015 leaves an ambiguity about what “obtained” means – whether a resource must be physically obtained by a company or simply surveyed by a company to claim rights to it. There are currently no additional bills being proposed in the U.S. to address these issues. More likely than not, Congress and the president will only consider these issues once the first company makes a claim. However, if that happens within the next decade, our next president may be put face to face with a conflict between U.S. economic interests and international law.

Asteroid mining raises huge questions technologically, economically, and legally. We still have a long way to go in developing the rockets, spaceships, and mining equipment for asteroid mining operations. In addition, we don’t yet understand how the infant space economy will develop and what demands it will create. Lastly, if we do develop the technology for an expanding space economy, nations may not even agree on the legality of asteroid mining. The future is unclear, but as we begin to deplete the Earth’s remaining resources, we may be dealing with these issues sooner rather than later.

Andy Greenspon is a Ph.D. candidate in Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences.

This post is part of our Special Edition: Dear Madam/Mister President.

For more information:

  1. For more information on near-Earth objects, see:
  1. To learn more about private companies involved in the newest rocket technology, see:,
  1. To learn more about the NASA asteroid sample return mission OSIRIS-REx, see:
  1. To learn more about the private companies developing asteroid mining technology, see:,
  1. For more considerations about law governing the use of space resources, see:





One thought on “Precious metals in peril: Can asteroid mining save us?

  1. Ayant aidé des milliers d’entrepreneurs avec les démarches liées à leurs entreprises, nous considérons que la comptabilité ne doit pas être un obstacle à quiconque souhaitant créer sa société.

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