Asteroid mining
Asteroid mining is the hypothetical extraction of materials from asteroids and other minor planets, including near-Earth objects.
Research missions focused on asteroid sample return, including Hayabusa, Hayabusa2, OSIRIS-REx, and Tianwen-2, illustrate the challenges of collecting ore from space using current technology. As of 2024, around 127 grams of asteroid material have been successfully brought to Earth from space. Asteroid research missions are complex endeavors that yield a tiny amount of material: less than 100 milligrams for Hayabusa, 5.4 grams for Hayabusa2, and approximately 121.6 grams for OSIRIS-REx, with Tianwen-2 mission currently ongoing.
These figures are comparatively negligible when considering the substantial investments and resources allocated to these projects.
Notable asteroid mining challenges include the high cost of spaceflight, unreliable identification of asteroids that are suitable for mining, and the challenges of extracting usable material in a space environment.
History
Prior to 1970
Before 1970, asteroid mining existed largely within the realm of science fiction. Publications such as Worlds of If, Scavengers in Space, and Miners in the Sky told stories about the conceived dangers, motives, and experiences of mining asteroids. At the same time, many researchers in academia speculated about the profits that could be gained from asteroid mining, but they lacked the technology to seriously pursue the idea.The 1970s
In 1969, the Apollo 11 Moon Landing spurred a wave of scientific interest in human space activity far beyond the Earth's orbit. As the decade continued, increasing academic interest surrounded the topic of asteroid mining. A sizeable portion of serious academic consideration was aimed at mining asteroids located closer to Earth than the main asteroid belt. In particular, the asteroid groups Apollo and Amor were considered. These groups were chosen not only because of their proximity to Earth but also because many at the time thought they were rich in raw materials that could be refined.Despite the wave of interest, many in the space science community were aware of how little was known about asteroids and encouraged a more gradual and systematic approach to asteroid mining.
The 1980s
Academic interest in asteroid mining continued into the 1980s. The idea of targeting the Apollo and Amor asteroid groups still had some popularity. However, by the late 1980s, the interest in the Apollo and Amor asteroid groups was being replaced with interest in the moons of Mars, Phobos and Deimos.Governmental organizations and space agencies, such as NASA, begin to formulate ideas of how to process materials in space and what to do with the materials that are hypothetically gathered from space.
The 1990s
New reasons emerged for pursuing asteroid mining. These reasons tended to revolve around environmental concerns, such as fears over humans over-consuming the Earth's natural resources and trying to capture energy from the Sun in space.In the same decade, NASA was trying to establish what materials in asteroids could be valuable for extraction. These materials included free metals, volatiles, and bulk dirt.
The 2010s
After a burst of interest in the 2010s, asteroid mining ambitions shifted to more distant long-term goals, and some 'asteroid mining' companies pivoted to more general-purpose propulsion technology.On 24 April 2012, at the Seattle, Washington Museum of Flight, a plan was announced by billionaire entrepreneurs to mine asteroids for their resources. The company was called Planetary Resources, and its founders included aerospace entrepreneurs Eric Anderson and Peter Diamandis. The company announced plans to create a propellant depot in space by 2020, aiming to develop the process of splitting water from asteroids into hydrogen and oxygen to replenish satellites and spacecraft. Advisers included film director and explorer James Cameron; investors included Google's chief executive Larry Page, and its executive chairman was Eric Schmidt. Telescope technology proposed to identify and examine candidate asteroids lead to development of the Arkyd family of spacecraft; two prototypes of which were flown in 2015 and 2018. Shortly after, all plans for the Arkyd space telescope technology were abandoned; the company was wound down, its hardware auctioned off, and remaining assets acquired by ConsenSys, a blockchain company.
A year after the appearance of Planetary Resources, similar asteroid mining plans were announced in 2013 by Deep Space Industries; a company established by David Gump, Rick Tumlinson, and others. The initial goal was to visit asteroids with prospecting and sample return spacecraft in 2015 and 2016; and begin mining within ten years. Deep Space Industries later pivoted to developing & selling the propulsion systems that would enable its envisioned asteroid operations, including a successful line of water-propellant thrusters in 2018; and in 2019 was acquired by Bradford Space, a company with a portfolio of earth orbit systems and space flight components.
The 2020s
The 2020s have brought a resurgence of interest, with companies from the United States, Europe, and China renewing their efforts in this ambitious venture. This revival is fueled by a new era of commercial space exploration, significantly driven by SpaceX. SpaceX's development of reusable rocket boosters has substantially lowered the cost of space access, reigniting interest and investment in asteroid mining. A US congressional committee acknowledged this renewed interest by holding a hearing on the topic in December 2023. There are also endeavors to make first-time landings on M-type asteroids to mine metals like iridium which sells for many thousands of dollars per ounce. Private company driven efforts have also given rise to a new culture of secrecy obfuscating which asteroids are identified and targeted for mining missions, whereas previously government-led asteroid research and exploration operated with more transparency.Minerals in space
As resource depletion on Earth becomes more of a concern, the idea of extracting valuable elements from asteroids and transporting them to Earth for profit, or using space-based resources to build solar-power satellites and space habitats, becomes more attractive. Hypothetically, water processed from ice could refuel orbiting propellant depots.Although asteroids and Earth accreted from the same starting materials, Earth's relatively stronger gravity pulled all heavy siderophilic elements into its core during its molten youth more than four billion years ago. This left the crust depleted of such valuable elements until a rain of asteroid impacts re-infused the depleted crust with metals like gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium and tungsten. Today, these metals are mined from Earth's crust, and they are essential for economic and technological progress. Hence, the geologic history of Earth may very well set the stage for a future of asteroid mining.
In 2006, the Keck Observatory announced that the binary Jupiter trojan 617 Patroclus, and possibly large numbers of other Jupiter trojans, are likely extinct comets and consist largely of water ice. Similarly, Jupiter-family comets, and possibly near-Earth asteroids that are extinct comets, might also provide water. The process of in-situ resource utilization—using materials native to space for propellant, thermal management, tankage, radiation shielding, and other high-mass components of space infrastructure—could lead to radical reductions in its cost. Although whether these cost reductions could be achieved, and if achieved would offset the enormous infrastructure investment required, is unknown.
From the astrobiological perspective, asteroid prospecting could provide scientific data for the search for extraterrestrial intelligence. Some astrophysicists have suggested that if advanced extraterrestrial civilizations employed asteroid mining long ago, the hallmarks of these activities might be detectable.
An important factor to consider in target selection is orbital economics, in particular the change in velocity and travel time to and from the target. More of the extracted native material must be expended as propellant in higher Δv trajectories, thus less returned as payload. Direct Hohmann trajectories are faster than Hohmann trajectories assisted by planetary and/or lunar flybys, which in turn are faster than those of the Interplanetary Transport Network, but the reduction in transfer time comes at the cost of increased Δv requirements.
The Easily Recoverable Object subclass of Near-Earth asteroids are considered likely candidates for early mining activity. Their low Δv makes them suitable for use in extracting construction materials for near-Earth space-based facilities, greatly reducing the economic cost of transporting supplies into Earth orbit.
The table above shows a comparison of Δv requirements for various missions. In terms of propulsion energy requirements, a mission to a near-Earth asteroid compares favorably to alternative mining missions.
An example of a potential target for an early asteroid mining expedition is 4660 Nereus, expected to be mainly enstatite. This body has a very low Δv compared to lifting materials from the surface of the Moon. However, it would require a much longer round-trip to return the material.
Multiple types of asteroids have been identified but the three main types would include the C-type, S-type, and M-type asteroids:
- C-type asteroids have a high abundance of water which is not currently of use for mining, but could be used in an exploration effort beyond the asteroid. Mission costs could be reduced by using the available water from the asteroid. C-type asteroids also have high amounts of organic carbon, phosphorus, and other key ingredients for fertilizer which could be used to grow food.
- S-type asteroids carry little water but are more attractive because they contain numerous metals, including nickel, cobalt, and more valuable metals, such as gold, platinum, and rhodium. A small 10-meter S-type asteroid contains about of metal with in the form of rare metals like platinum and gold.
- M-type asteroids are rare but contain up to 10 times more metal than S-types.