字幕表 動画を再生する 英語字幕をプリント On the 15 February 2013, an asteroid entered Earth's atmosphere over Russia. It created a fireball brighter than the sun. Its shockwave injured more than one thousand people. Videos like this show why asteroids pose a great threat to life on Earth, but they are also the reason why some see them as a golden opportunity. This clip was watched millions of times on devices like this. Such small and powerful machines are built with precious metals like gold, silver, and platinum. These rare resources are not just pretty, they are among the most conductive, durable and malleable of all elements. They are highly important for medicine, aerospace, and technology. But getting them is an ugly process. Mining destroys entire ecosystems, displaces communities, and creates toxic waste. And there's a tragic irony: platinum is used to make solar panels, hydrogen, and wind turbines. So, the more the world goes green, the more toxic mining it needs. But our planet is not the only source of these special elements. The key to sparing Earth this devastating mining may lie in the planet's ultimate threat: asteroids. Meet Lucy, a star nicknamed after the famous Beatles' song. That's because Lucy's core is likely made of crystallized carbon. Alas, it is a giant diamond the size of our sun. The sky certainly is no longer the limit in space. This is Chris Lewicki. He was the co-founder and “chief asteroid miner” of Planetary Resources, the first company with the explicit goal of mining asteroids. He even has an asteroid named after him. I am very grateful to have 13609 Lewicki named in my honor. Lucy is too far away to reach. But other celestial bodies closer to Earth are just as incredible. Platinum and gold are very heavy and over time they sank into the planet's core. That's why they are they are so rare on the Earth's crust. But again because asteroids don't have much gravity, that didn't happen on asteroids and in some cases, they are a hundred times as concentrated. In 2015, for example, an asteroid that passed close to our planet was estimated to contain more platinum than has ever been mined on our planet. Or take 16 Psyche, a metal world estimated to be worth 700 quintillions of dollars. Until now, this was all just theoretical because space travel was just too expensive. But that's changing. A seat on a SpaceX rocket is three times cheaper than it was on the Space Shuttle. This has started a new gold rush. In 2012 Larry Page, the co-founder of Google, put his wealth behind Planetary Resources. The year after, a new company joined the race to mine asteroids. And in 2017 NASA announced it would pay a visit to Psyche. We will get there. She is Lindy Elkins-Tanton, and she is the one leading NASA's Psyche mission. An important thing to note is that the Psyche mission that I'm running is a pure science mission. But although the program has no relation to asteroid mining, it could lay the groundwork for the first step in the asteroid mining playbook: Choosing an asteroid. The kind that you are interested in are the kind that have an orbit very similar to the Earth's own orbit. Most asteroids orbit the sun between Mars and Jupiter in the asteroid belt. But some of them sometimes pass close to Earth. But you also gonna wanna make sure that it's big enough. The ideal size is probably a couple hundred meters across, something maybe the size of a city block. So it's not huge, but it's also not tiny. Then you have to get to the asteroid. And here there is some good news. Asteroids are really the low hanging fruit of the solar system. They might be physically far away most of the time, but the amount of energy that it takes to get to an asteroid is a lot less than it is to land on the Moon or Mars. And that's because asteroids have very little of their own gravity which means you don't have to spend a lot of energy to land on the surface, and you don't have to spend a lot of energy to back get off the surface. Then comes the real mining, and here it gets tricky. You can't just use a pickaxe on an asteroid because its gravity is so tiny that your gold would float away. But different elements melt at different temperatures, so miners can heat them up, and then separate them using gigantic mirrors to concentrate sunlight. You apply heat, you evaporate the material, and in the process of doing that you can separate the stuff you don't want, and concentrate the things that you do want, and condense them back out. Crazy as it sounds, mining asteroids might not only be feasible, but also much more sustainable than mining Earth. This is a very interesting point and the point which interestingly has been overlooked in the past literature. He is Andreas Hein, a researcher who has actually crunched the numbers! And it actually turns out that the answer seems to be yes! He estimates that the rocket fuel necessary to go and bring back one kilogram of platinum from an asteroid would release 150 kilograms of CO2. On the other hand terrestrial mining would generate 40,000 kilos of CO2. Mining asteroids could be hundreds of times more sustainable. Essentially the main reason is there is almost no other substance you can mine which generates that much greenhouse gases. Outsourcing mining to space would decrease pollution on Earth. But there is an economic problem. In terms of sustainability, it's a gigantic win. In terms of economics, it's not profitable yet. The problem if you mine five times of the platinum you have on Earth, right now, it means that the market prices will immediately crash. You can sell it at a much lower price, which means that you are diminishing your profit margin. So you are operating your infrastructure at a loss, and that makes that very unattractive for investors. Carbon taxes and new technologies could change this equation, but it would still take several years for space mining to become profitable. Investors decided to not wait so long. The world doesn't quite support a business model that takes more than a hundred million dollars and more than ten years to make a return on an investment, and maybe it should. Lewicki's company failed to raise enough funds, forcing it to abandon its goal of mining asteroids. Planetary resources didn't succeed in their ultimate goal to mine asteroids. But I think it succeeded in a lot of ways of the steps to get there. There wasn't much gold in California, after all. But yesterday's settlers succeeded in something else, although with great harm to the indigenous population. In the rush to get to the frontier, they accelerated the development of the West. Today's space miners are doing something similar. We are, as a world, a lot closer to using resources from space than we were when the company was founded in 2009. You now can get a degree in space mining! The business case doesn't quite yet close. But we could make it get there, we can find a way. And I think it is in some ways the inevitable future of human kind because we can't resist. It's been our history as long as we've been able to track it going backwards that humans are explorers. New technologies can make space mining economical. Just a few decades ago, the very technology you're using to watch this video seemed impossible. Today, we can use satellites to beam the internet everywhere on the planet. In 10, 15, or 20 years a lot can happen. One day, mining Earth may seem obsolete. A bit like using candles to light up your room. That would be the beautiful goal, that is the utopian future of humankind where we have learned to take care our Earth and we can do our heavy industry and our mining and mineral extraction in space. 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