Asteroid Types and Compositions: A Guide to Space Resources

Returning 20 tons of gold from NEAs could net $1.5 billion, but Earth already mines several thousand tons annually, so one mission won't crash markets. Prices move on expectation as much as actual deliveries, and working mines signal future supply could arrive by hundreds of tons. Multi-year return times carry risks of accidents, theft, or loss. After accounting for production costs ($40M/ton), insurance, and delayed payment, miners might prefer selling gold upon departure for $62M/ton rather than waiting. Prices would drop toward production and shipping costs over time. However, the real near-term value lies in industrial materials for orbital construction: bulk metals (iron, nickel, aluminum, titanium), regolith, and water ice. Moving these from Earth at current costs would be ruinous, but in-situ processing from asteroids makes megastructures feasible. Volatiles like water, ammonia, and carbon dioxide serve dual purposes: rocket propellants (when cracked into oxygen and hydrogen) and feedstock for agriculture and industry. Phosphorus, essential for fertilizers and increasingly scarce on Earth, may be found in accessible asteroids. Once established in space with in-situ fuel production, shipment costs might reduce to just reentry pod creation and electrolysis of water to phosphorus. This transforms what seems like an exotic luxury mission into a loss-leader paying for infrastructure to tap the real prize: permanent, local supply of everything needed to live and build in space.

Space mining offers a viable alternative to terrestrial mining by providing abundant critical metals (such as platinum group metals) at potentially lower costs and with reduced environmental impact; a single kilometer-diameter metallic asteroid could contain approximately 117,000 tons of platinum—equivalent to 688 years of global supply—making it economically attractive despite the high initial investment required for space missions.

Near-Earth asteroids contain diverse resources including industrial metals, water, platinum group metals, silicon, and silicate gravel. With 9,500 known asteroids and 1,000 new discoveries annually, approximately 1,700 are more accessible than the Moon. A typical ton of asteroidal rock is worth $1 million in orbit versus $4,000 on Earth due to launch costs. Mining processing involves crushing, separation, and collection adapted for zero-gravity. The microgravity foundry prints high-strength nickel parts on demand using asteroid nickel-iron grains, recycled metal, or other nickel sources with no consumables except nickel. Applications include repairing equipment in deep space, manufacturing habitats, solar power satellites, and custom parts from schematics.

Asteroids contain three valuable resource categories: water for life support and rocket fuel production, metals for in-situ construction reducing Earth launch costs ($1,000/pound), and platinum group metals for Earth markets. Water splitting produces hydrogen and oxygen for propulsion. Building structures in space using local materials is economically superior to launching from Earth. Companies envision providing infrastructure for future lunar and Martian colonies, supporting long-term human space settlement goals.

Asteroid mining offers astronomical resource quantities compared to Earth mining. Even small asteroids (1 km) contain trillions of tons of metals. The primary economic advantage is in-space utilization: materials already in space avoid launch costs, making asteroid resources far more economical for space infrastructure than Earth-sourced materials. This cost benefit enables building space stations, Mars bases, and other structures more efficiently.

In June 1936, a person declared ownership over all extraterrestrial objects, which was legally invalid. In 1967, an international treaty on space was signed, prohibiting the use of nuclear weapons and establishing the basic legal framework for space. The declaration was signed by 114 countries worldwide, meaning all space is a common heritage of humanity and must be managed collectively by all countries. Therefore, it is no longer possible to acquire all extraterrestrial objects as private property.

Three key treaties govern space: the 1967 Outer Space Treaty (100+ signatories), the 1979 Moon Treaty (France and India signed, major powers did not), and the recent Artemis Accords. The Moon Treaty prohibits private claims to celestial bodies and recognizes space resources as humanity's common heritage. The Artemis Accords apply only to private companies acting on behalf of states, creating jurisdictional gaps. Major spacefaring nations have been reluctant to join, citing concerns about US-centric governance and lack of binding obligations.

The Artemis Accords represent a voluntary framework for space governance that addresses the critical question of property ownership in outer space, which the 1967 Space Treaty did not adequately resolve; unlike the UN's voluntary registration system for space objects, the Accords establish principles for equitable property rights among participating nations and private companies, while preserving historic space sites and artifacts, though enforcement ultimately depends on Earth-based authorities rather than space-based mechanisms.

The US Space Resource Exploration and Utilization Act of 2015 is the first national law providing a conceptual difference from the Outer Space Treaty. It introduces the term 'space resource,' which is not in the UN treaty. The Outer Space Treaty has only one term 'natural resources of celestial bodies,' but introducing new terms might mean something is different and could cause questions about whether Outer Space Treaty obligations apply to asteroid resources. The Artemis Accords are bilateral agreements between NASA and countries including Australia, Canada, Italy, Japan, Luxembourg, UAE, UK, Argentina, and Bahrain. These agreements represent a new trend where major space actors create bilateral frameworks for space resource exploration. The legal innovations include: principles reaffirming Outer Space Treaty provisions; technical provisions on interoperability; principles internationalizing the US national legal approach; and provisions related to natural resources including safety zones. The safety zones provision allows the first come, first served principle and establishes zones that can only be accessed through special arrangements, potentially contradicting the Outer Space Treaty's free access principle. The key question is whether the legal regime of natural resources of celestial bodies will be multilateral and universal according to the Outer Space Treaty, or whether it will be bilateral based on agreements like the Artemis Accords (with about 30 states parties) or national legal approaches. If different states follow different patterns (US and partners, Russia and partners, China and partners), clashes regarding exploitation of natural resources might be inevitable. The goal is to prevent such interstate clashes, similar to how humanity managed to prevent interstate clashes regarding natural resources of the world ocean. This requires comprehensive discussion of the interests of all states, particularly developing countries, before exploration activities begin. The concept of common heritage of mankind, as reflected in the Moon Agreement, has both negative and positive assessments, and states today have some reservedness regarding the realization of this concept. The development of international space law involves political dynamics where major space powers have advantages, with the United States having more than 100 states parties to the Outer Space Treaty while only about 30 states are parties to the Artemis Accords.

Five international treaties govern space activities: the Outer Space Treaty, Rescue Agreement, Liability Convention, Registration Convention, and Moon Agreement. The Outer Space Treaty establishes that space, including the Moon, cannot be appropriated by any nation and must be used for peaceful purposes. States bear international responsibility for all space activities conducted by their citizens or companies. The Artemis Accords, established in 2020, represent a new framework for lunar exploration, allowing resource utilization and establishing 'safety zones' around exploration activities. Critics argue this could lead to territorial claims similar to historical colonization, raising concerns about equitable access to space resources.

NASA's OSIRIS-REx mission successfully returned samples from asteroid Bennu on September 24, 2023, after a 7-year journey covering 6.4 billion km. The samples contain water and carbon, essential elements for life, suggesting these building blocks may be common throughout the universe. Bennu, a 490-meter asteroid with a 1 in 150 collision probability with Earth in 300 years, is classified as a Type B asteroid containing primitive organic molecules. Japan's Hayabusa2 mission returned samples from Ryugu containing uracil, a nucleobase in RNA. NASA's Psyche mission launched October 13, 2023, using SpaceX Falcon Heavy, will reach asteroid 16 Psyche (280 km × 232 km) in 2029. Psyche, potentially the core of an ancient failed planet, contains iron, nickel, and gold worth an estimated 1000 quadrillion dollars. The mission will map the asteroid for 21 months to understand planetary formation processes.

NASA's OSIRIS-REx mission successfully returned 150-350 grams of asteroid Bennu soil samples to Earth on September 25, 2023, after collecting them in October 2020 using a touch-and-go maneuver; the mission collected more material than planned (60 grams), requiring rapid packaging to prevent sample loss. Meanwhile, the Psyche mission will study the metal-rich asteroid Psyche by using radio signals to track the spacecraft's position and measure gravitational effects, allowing scientists to infer the asteroid's internal structure without direct sampling.

Two major missions are collecting asteroid samples this year: NASA's OSIRIS-REx and Japan's Hayabusa 2. OSIRIS-REx will study asteroid Bennu for one year, create a precise map to select the sampling site, and return samples by September 2023. Hayabusa 2 has arrived at asteroid Ryugu and faces challenges with its laser altimeter, which cannot accurately measure altitude over the dark, carbon-rich surface. Despite this, Ryugu's mass of 450 million tons provides sufficient surface gravity (1/81 billionth of Earth's) for lander operations. The mission aims to deploy a rover and French-German lander, demonstrating international cooperation in space exploration.

The 2010s brought increasingly sophisticated sample return missions. JAXA's Hayabusa2 (completed 2020) successfully returned samples from asteroid Ryugu, revealing it formed in extreme heat above 1,000°C and broke from a larger parent body. The mission discovered carbonated liquid water inside iron sulfite crystals—a 'soda-like' substance containing salts and organic matter. NASA's Osiris-Rex then achieved an unprecedented 250-gram sample collection from asteroid Bennu, 50 times heavier than any previous asteroid sample. Both missions confirmed asteroids are rubble piles from ancient collisions, not solid rocks, and demonstrated that spacecraft can sink into asteroid surfaces as if they were dust.

Two major missions are returning asteroid samples to Earth: Hayabusa 2 (JAXA) landed on Ryugu in February 2019 after a 3.5-year journey, collecting surface material by firing projectiles and planning explosive cratering for deeper samples. OSIRIS-REx (NASA) visited Bennu in December 2018, using moment of inertia measurements on its sample arm to quantify collected material. Both missions compare near-Earth asteroids to understand solar system formation, with samples returning in 2020 and 2023 respectively.