An astrophysicist has questioned whether mining in outer space is really as commercially feasible as it appears.
In the last couple of years, numerous start-up companies, including one comprising Sir Richard Branson, have announced plans to extract resources from space rocks. In 2012, Planetary Resources and Deep Space Industries backed by billionaire investors including Hollywood director James Cameron and Google executives Larry Page and Eric Schmidt unveiled their vision of using low cost robotic spacecraft called Fireflies and Dragonflies to squeeze the chemical components of fuel as well as minerals out of near-Earth asteroid rocks.
Caterpillar also recently announced that it was working with NASA on a multi-terrain loader that could conceivably be used in mineral extraction on the moon and on asteroids.
Calculations by Dr Martin Elvis, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, US, now suggest our cosmic neighbourhood might not be a treasure trove after all. The Harvard astrophysicist argues just 10 near-Earth asteroids might be suitable for commercial-scale mining.
Searching for platinum
Elvis developed an equation to estimate the number of asteroids in the solar system that could be exploited in a cost-effective way. He assumed that mining operations would want to focus on iron-nickel asteroids (known as M-type), considered the most promising targets for finding platinum group metals. These include platinum, along with iridium, palladium and others.
These metals are rare in the Earth’s crust, with platinum and palladium the most economically important. But according to the analysis, just one per cent of near-Earth asteroids are rich in these elements.
The size of the target is also a factor; the paper suggests it wouldn’t be worth mining asteroids smaller than about 100m because the total value of the ore they would produce wouldn’t be enough to cover the costs.
Eric Anderson, the co-founder of asteroid mining company Planetary Resources, pointed to what he said were key errors in Elvis? study. “Number one, the author points to an assumption of only wanting to go to M-type asteroids,” he said. “Assuming we were only going after platinum group metals, the most platinum-rich asteroids are the C-class ones.
“I think the study is probably off by a factor of 100, conservatively, and I think it’s off by a factor of 1000 optimistically,” Anderson added. “We’ve been studying this with some of the brightest people in the world for the last three years. We are intimately familiar with the risks and other factors.
“We have only discovered one per cent of the asteroids in the solar system and we are discovering them at a larger and larger rate. We discover two or three asteroids a day. If we get from one per cent to 10 per cent, then the 650,000 asteroids we have discovered jumps to 6.5 million.”
The analysis also looked at the number of asteroids that could be profitably mined for water, which could be used in space for life support or separated into hydrogen and oxygen for rocket fuel. The number of suitable water-bearing asteroids larger than 100m was around 18.
Unknowns and uncertainties
Prof Alan Fitzsimmons from Queen’s University Belfast, UK, who was not involved with the study, said the calculations were “plausible” but that he would have placed even more emphasis on the uncertainties.
“The make-up of small near-Earth asteroids is still relatively unknown,” Fitzsimmons said. “There are large uncertainties in the total number of platinum group-rich asteroids that come near the Earth. This is because it is still difficult to unambiguously determine the mineral make-up of small asteroids.
“We know they exist, as pieces are found as meteorites on Earth. The small asteroid that formed Meteor Crater in Arizona some 50,000 years ago was one such object.”
Elvis? paper is published in the Journal of Planetary and Space Science.
Source: BBC News Science & Environment