Asteroids are a class of small rocky and metallic bodies orbiting the sun. These bodies represent the remains of failed planetesimals, or proto-planets (Asphaug, 2003) & (Binzel & Barucci, 1991). Asteroid composition varies widely, from volatile-rich bodies to metallic bodies with high concentrations of rare metals such as gold, silver, and platinum in addition to more common elements such as iron and nickel. Platinum-rich asteroids may contain grades of up to 100 grams per ton, 10-20 times higher than open pit platinum mines in South Africa (Sonter, 2006). These ore grades mean that one 500-meter-wide platinum-rich asteroid could contain nearly 175 times the annual global platinum output, or 1.5 times the known world reserves of platinum group metals ("Asteroid composition", 2012). Asteroid mining is a proposed approach to mining critical elements from these small bodies. Because of the difficult nature inherent to mining asteroids, few companies or governments are currently considering asteroid mining. At present, only one company, Planetary Resources, is conducting research into the technologies and strategies necessary to make asteroid mining economical. Our current understanding of asteroid composition confirms they are a likely source of many critical elements, such as the platinum group elements. However, asteroid mining is currently only viable as a long-term solution; currently, the infrastructure and techniques needed to mine and refine asteroid resources is under development, making short term returns unlikely for mining companies.
Planetary Resources and the Keck Institute for Space Studies (KISS) have independently conducted feasibility studies for asteroid mining and retrieval ("Asteroid Mining Venture", 2012) & ("Is Asteroid Mining Possible?", 2012). Japan conducted a successful sample return mission to the asteroid Itokawa, an important stepping stone towards future sample of asteroid retrieval missions (JAXA, 2012). The Hayabusa mission to this asteroid was able to autonomously approach, land on, collect data on the surface and topography,and collect a sample of the Itokawa asteroid and return to earth to drop the sample containing capsule in Australia.
Asteroid mining shows promise as a method for obtaining critical elements. The asteroid belt in our solar system contains ~8% metal-rich (M type) asteroids and 75% volatile-rich carbonaceous (C type) asteroids ("Asteroid belt", 2010). The denser metals in asteroids, including platinum group minerals and REE's, are distributed relatively evenly throughout the asteroid body, simplifying the mining process as drilling can be relatively shallow (i.e. not into the core) for ore grades to be surprisingly high.
At present, asteroid mining is a highly speculative technique; the research and technology to successfully exploit these mineral resources is still under development. Challenges include categorization and identification of mineable deposits, building the infrastructure to mine and refine asteroid material, and creating the ability to move mined material onto earth. Current proposals suggest placing processing facilities in earth or lunar orbit with regular access service to the asteroid belt (Tomaswick, 2012). The remoteness of these facilities will make them difficult to create and maintain, requiring significant advances in robotic technology. Asteroid mining is a technology in its earliest stages with massive start-up costs. Other sources of strategic elements may be discovered and alternative technologies may reduce demand before asteroid mining becomes a reliable source of strategic elements.
According to the KISS study, the cost for a future mission to identify and return a 500 ton asteroid to low earth orbit is ~$2.6 billion USD, ignoring the costs to develop the infrastructure necessary to process the materials in the asteroid ("Asteroid usage", 2012). However, Planetary Resources estimates that a single 30 meter long platinum-rich asteroid could contain $25 to $50 billion USD worth of platinum at today's prices (Klotz, 2012). Clearly, once the proper infrastructure is in place, there is potential for significant profit. Currently, research into the feasibility of human and robotic missions to asteroids is being conducted by both governmental organizations (JAXA, NASA) and private companies (Planetary Resources).
The KISS study claims that it will be feasible to "identify, capture, and return" an asteroid seven meters in diameter and 500,000 kg in weight using technology that could be developed in the next decade (48). This study states that asteroid mining is feasible as long as three major advances are in place- development of an efficient solar/electric propulsion system, development of a campaign to discover and target potential asteroids, and the establishment of a human presence in lunar orbit ("Is Asteroid Mining Possible?", 2012).
Although asteroid mining is capable of producing significant amounts of critical elements, Mission 2016 recommends that funding for asteroid mining come from the private sector. At present, the high start-up costs, high risk, and long timescales on investment returns make it difficult for governments to safely invest in asteroid mining. Since some resources are projected to become critically low very soon, Mission 2016 suggests that governments focus on more easily available resources and technologies.
2012-2025: Launch of space probes and telescopes to prospect and collect data on near earth asteroids, such as the LEO Space telescope and the ARKYD Series 100 Interceptor, and ARKYD Series 300 Rendezvous Prospector ("Technology," 2012)
2025-2035: NASA lands an astronaut on an asteroid
2035-2045: Space development and infrastructure necessary to further space exploration and exploitation
2045+: Asteroid mining prospers, as well as humankind's expansion in space
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