I'm a little confused. How can earth be running short of some metals if the smallest metal-rich near earth asteroid holds more platnium gold and nickel than has been mined in human history? For surely these asteroids have been smacking into earth for billions of years? Wouldn't it be easier to find some that have smacked into the earth and mine them?One problem is that the Earth is distressingly uncooperative when it comes to preserving asteroid impacts. Erosion, continental drift, subduction, etc. all conspire to a) do away with asteroid impact zones, and b) hide the ones that survive. Still, there are still some well-known mineral deposits that are probably asteroid-derived. For example, the South African gold strike was asteroid-desposited, as was the Sudbury nickel deposit (probably.) The more important question, though, is this:
And although metal meteorites found on earth do contain some gold and platinum and other expensive metals, it's a tiny amount per kilo and isn't concentrated in one spot as can be the case with metal deposits on earth, so it would be a very difficult process to get say the gold out of a metal rich asteroid.So how do we get useful amounts of metal out of an metal-rich asteroid?
It turns out, it's not that hard. An average metal-rich asteroid is composed mostly of Iron and Nickel. Usually, these two elements make up more than 90% of the rock. The rest is often platinum-class metals. Fortunately, separating this stuff out is actually very easy using carbonyl chemistry. Essentially, exposing certain metals (iron, nickel, platinum, chromium, gold, some others) to carbon monoxide at high pressures gives you a carbonyl form of the metal - iron carbonyl, nickel carbonyl, etc. (These all have proper names, but I forget them at the moment.) With carbonyls, it is possible to a) separate out metals, and b) refine them to very, very high levels - 99.9% on the first pass is not unheard of. Carbonyl chemistry is used here on Earth to separate and refine nickel. Inco in Sudbury uses carbonyl chemistry all the time. It requires relatively little energy or equipment. Bring a small supply of carbon monoxide, and you're set.
I think by the time we're able to get to the asteroids, there won't be any difficulty in actually using them.
The real problem is getting the metals back to Earth. For that, we need a much more reliable and cheap access to space than we have so far.
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I'm afraid I'm still a little confused. If an average metal rich asteroid is 90% iron and nickel and the rest is often platinum class metals, then with the price of platinum at around $1,000 U.S. dollars per ounce, a one ton metal meteroite could be worth $30,000,000 or more.
Since the sale price of metal rich meteorites don't come anywhere near this value I think you may have picked up some wonky figures from somewhere. In fact I've never heard of anyone melting down a meteorite to make money. I was always under the impression that very valuable metals were present only in trace amounts.
And I also thought that the Vredefort Dome impact in South Africa led to severe folding and faulting of the crust that resulted in the rich gold deposits, but the gold was already in the earth and didn't come from the meteorite?
But I could be wrong.
re: South Africa - I may have been misinformed on that one. Apologies.
One clarification - I'm talking about mining asteroids, in space, not smelting meteors here on Earth. You're right, a 1-ton meteor would be uneconomical to process.
However, a 2-km or larger asteroid (Amun, the near earth asteroid that gives the $20 trillion figure, is about 2 km long) would have billions of tons.
The objective with a rock that big would be building and launching equipment that was small and automated enough to return useful amounts of metal.
(While we've focused on the pretty shiny metals, it's worth pointing out that Iron and Nickel would still have great value in space construction.)
Most books by reputable space scientists (John S. Lewis, Robert Zubrin, etc.) indicate that an umanned mission could, if it was reusable, eventually pay-off its initial investment several times. Of course, these conclusions are based on assuming the ability of technology we don't yet have.
Probably the best book on this subject is "Mining the Sky" by John S. Lewis. I'm really, really not making this stuff up.
I guess that mining asteroids and stuff will probably be very important for construction in space, but I doubt that transporting materials from space to earth will turn out to be very important. My guess is that as our technology advances and makes asteroid mining practical, advanced technology will also make it easier to detect and extract resources on earth. I also guess (As you can see I like to guess a lot) that in the future we will use less metals and more carbon based substances as our materials technology progresses. But I think it's possible that the earth could import energy from space.
I've found your posts very interesting and I've enjoyed thinking about these matters. Thanks.
I've done some calculations on the value of the Amun asteroid and I only get about a third of the price per ton that the 20 trillion dollar figure represents. If you're interested you can check out the post I wrote about it on my blog.
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