The prospects for mining precious metals and structural materials from asteroids

Artist impression of an asteroid smelting operation. Credits: Bryan Versteeg / spacehabs.com

When humanity migrates out into the solar system we’ll need a variety of elements on the periodic table to build settlements and the infrastructure needed to support them such as solar power satellites. But before that future becomes a reality, there may be a near term market on Earth for precious metals sourced in space as transportation costs come down. There is also the added benefit of moving the mining industry off planet to preserve the environment. Could the asteroid belt provide these materials? Kevin Cannon, assistant professor at the Space Resources Program at the Colorado School of Mines describes the prospects for mining precious metals and building materials for space infrastructure asteroids in a recent paper in Planetary and Space Science. Coauthors on the paper Matt Gialich and Jose Acain, are CEO and CTO, respectively, at the asteroid mining company AstroForge which just came out of stealth mode last year.

The asteroids have accessible mining volume that exceeds that available on the Moon or Mars. This is because only the thin outer crust of these bodies is reachable by excavation, whereas the asteroids are small enough to be totally consumed resulting in higher accessible mining volume.

To-scale accessible mining volume of terrestrial bodies, calculated as the total volume for the asteroids (main belt mass of 2.39 x 1023 kg, mean bulk density of 2000 kg/m3), and as the volume for an outer shell 1.2 km in thickness for the Moon, Mercury, and Mars, equivalent to the deepest open pit mine on Earth. Note the combined volume of the near-Earth asteroids (~5 x 1012 m3) is too small to be visible at this scale. Figure 1 in paper. Credits K.M. Cannon et al.

The authors take a fresh look at available data from meteorite fragments of asteroids. Their analysis found that for Platinum Group Metals (PGMs), the accessible concentrations are higher in asteroids than ores here on Earth making them potentially profitable to transport back for use in commodity markets.

“Asteroids are a promising source of metals in space, and this promise will mostly be unlocked in the main belt where the Accessible Mining Volume of bodies greatly exceeds that of the terrestrial planets and
moons”

PGMs are indispensable in a wide range of industrial, medical, and electronic applications. Some examples of end-use applications include catalysts for the petroleum and auto industries (palladium and platinum), in pacemakers and other medical implants (iridium and platinum), as a stain for fingerprints and DNA (osmium), in the production of nitric acid (rhodium), and in chemicals, such as cleaning liquids, adhesives, and paints (ruthenium).

It has been pointed out by some analysts that flooding markets here on Earth with abundant supplies of PGMs from space will cause prices to plummet, but the advantage of reducing carbon emissions and environmental damage associated with mining activities may make it worth it. The authors also point out that there are probably various uses where PGMs offer advantages in material properties over other metals but are not being used because they are currently too expensive.

Asteroids are rich in other materials such as silicon and aluminum which would be economically more useful for in-space applications. As the authors point out, some companies are already planning for use of metals and manufacturing in space such as Redwire Corporation with their On-Orbit Servicing, Assembly and Manufacturing (OSAM) and Archinaut One, which will attempt to build structural beams in LEO. Another example mentioned in the paper has been covered by SSP: the DARPA NOM4D program with aspirations to develop technologies for manufacturing megawatt-class solar arrays and radio frequency antennas using space materials. Finally, another potential market for aluminum sourced in space is fuel for Neumann Thrusters (although spent upper stage orbital debris may provide nearer term supplies). And of course, silicon will be needed to fabricate photovoltaic cell arrays for space-based solar power.

AstroForge will test their asteroid mining technology on two missions this year. Brokkr-1, a 6U CubeSat just launched on the SpaceX Transporter 7 mission last April, will validate the company’s refinery technology for extracting metals by vaporizing simulated asteroid materials and separating out the constituent components. Brokkr-2 will launch a second spacecraft on a rideshare mission chartered by Intuitive Machines attempting their second Moon landing later this year. Brokkr-2 will hitch a ride and then fly on to a target asteroid located over 35 million km from Earth. The journey is expected to take about 11 months and will fly by the body and continue testing for two years to simulate a roundtrip mission.

NewSpace features the dawn of the age of space resources

Illustration showing concept of operations of the RedWater mining system for water extraction on Mars developed by Honeybee Robotics. Credits: Mellerowicz et al. via New Space

The editorial in the latest issue of New Space, coauthored by two of SSP’s favorite ISRU stars, Kevin Cannon and George Sowers, describes the dawning age of space resource utilization. Cannon, who guest edits this issue, and Sowers are joined by the rest of the leadership team of the graduate program in Space Resources at the The Colorado School of Mines: Program Director Angel Abbud-Madrid and professor Chris Dreyer. The program, created in 2017, has over 120 students currently enrolled. These are the scientists, engineers, economists, entrepreneurs and policymakers that will be leading the economic development of the high frontier, creating the companies and infrastructure for in situ resource utilization that will enable affordable and prosperous space settlement.

How can regolith on the Moon and Mars be refined into useful building materials? What are the methods for extracting water and oxygen from other worlds for life support systems and rocket fuel? Is it legal to do so? Will private property rights be granted through unilateral legislation? What will space settlers eat? The answers to all these questions and more are addressed in this issue, many of the articles free to access.

One of my favorite pieces, the source of this post’s featured image, is on the RedWater system for harvesting water on Mars. This technology, inspired by the proven Rodwell system in use for sourcing drinking water at the south pole, was developed by Honeybee Robotics, just acquired by Blue Origin earlier this year. End-to-end validation of the system under simulated Mars conditions demonstrated that water could be harvested from below an icy subsurface and pumped to a tank up on the surface.

We need to start thinking about these technologies now so that plans are ready for implementation once a reliable, affordable transportation system comes on line in the next few years led by companies such as SpaceX and others. Sowers has been working on thermal ice mining on cold worlds throughout the solar system for some time, predicting that water will be “the oil of space”. Cannon has been featured previously on SSP with his analytical tools related to lunar mining, the Pinwheel Magma Reactor for synthetic geology and plans for feeding millions of people on Mars.

Where should we get oxygen on the Moon?

Artist impression of activities at a Moon Base which could include oxygen production. Credits: ESA – P. Carril

Kevin Cannon of the Cannon Group at the Colorado School of Mines can help find the answer. In a recent post on his Planetary Intelligence blog, the Assistant Professor of Geology and Geological Engineering describes a trade study comparing extraction of oxygen from regolith such as Metalysis’ ESA funded study to getting O2 from ice mining at the lunar poles as favored by NASA. Nothing stands out from a cursory look at the pros and cons of each approach.

In a more data driven analysis to compare apples to apples, Cannon examines energy costs of mining oxygen and plots it against the amount of bulk material that has to be processed to produce an equal amount of O2 from different sources ranging from plain silicate regolith to various grades of water ice endmembers. The analysis even includes processing material from various types of asteroid resources. The types of ice/regolith mixtures can vary widely as described in one of Cannon’s tweets.

Artist’s impression of different types of water ice / regolith endmembers. Credits: Lena Jakaite / strike-dip.com / Colorado School of Mines

Cannon’s analysis reaches the conclusion that “At 1.5-2% water by weight, icy regolith is essentially on par with O2-from-regolith on a joule for joule basis. In other words, if you had a pile of icy regolith already sitting on the surface, it makes sense to throw it out if the grade is less than about 1.5% and extract oxygen directly from the silicate regolith instead.”

More brilliance from the mind of Kevin Cannon can be found in these posts: Want to eat like a Martian in an environmentally friendly manner?, The logistics of dining off Earth, SpaceX will need suppliers for Mars settlement, The accessibility of lunar ice. And of course, don’t forget to visit kevincannon.rocks.