By Martin Elvis

With the 2021 boom in space tourism and the rapid development of the giant SpaceX Starship from a string of fiery crashes to a ready-for-orbit vehicle, the idea that lots of people may soon live and work in space has become something that feels like it could happen, and potentially soon. That means harnessing resources beyond Earth. Is that desirable? Is it ethical?

It may be a surprise looking at images of the barren Moon or grey potato-shaped asteroids, but there are plenty of resources in space. Water is plentiful in space, and so is solar power to break the water down into its components, like oxygen, so we can breathe. Astronauts have grown salad vegetables on the International Space Station, and just recently, they harvested their first chili peppers, a foretaste of true space cuisine.

There are also huge amounts of precious metals in space, though for now, extracting them cheaply is a challenge. There are even greater amounts of iron, which would be needed to build giant space stations or cities in space. The asteroid belt, between the orbits of Mars and Jupiter, is the main repository of this abundance, containing about 10 million times the iron that is in Earth’s known reserves.

If profits shower down from space resources, then the economy in space will also grow—potentially exponentially. Eventually, as Jeff Bezos often says is his goal, there could be a trillion people living in space cities with only a minority living on planets.

What would the consequences of that growth be? My ethicist colleague, Tony Milligan, and I, an astrophysicist, looked into this. We found that for the next few centuries, exploiting space wealth could lead to a “post-scarcity” economy with plenty for everyone, and robots could do the chores, so we won’t need to work to survive. However, after that about 400 years from now, if we extrapolate the 20-year current world doubling rate of iron use, this currently rich economy will come to another major crisis: we will run out of iron.

Exponential growth has a way of reminding us that vast does not mean infinite. Doubling every 20 years, it takes over 300 years to use even 1/8th of the iron in the asteroid belt. But just three 20-year intervals take us to ¼, ½, and then 100% of supplies: It is completely gone at that point. That means we would need a tripwire to tell us that trouble was around the corner. We settled on “the 1/8th Principle”:

“We should regard as ours to use no more than one-eighth of the exploitable materials of the Solar System. By ‘ours’ we mean humanity’s as a whole, rather than any particular generation of humans or group of generations. The remaining seven-eighths of the exploitable Solar System should be left as space wilderness.”

Ideally, we would want more than a 60 years warning time, but it’s a feature of exponential growth that small changes in how we extrapolate forward in time become large changes in the predicted exhaustion date. If we set our tripwire at 1/16th or 1/32nd, we could be accused of crying wolf.

Recycling helps but only postpones the reckoning. If a society knows about the 1/8th Principle, that could offer an incentive to conserve and recycle resources. But if most people are by then living in space cities made of the iron that we want to recycle, they may object to having their homes recycled.

What about more remote resources? The Solar System is much bigger than the asteroid belt. But going out to the next great store of resources, the Kuiper Belt beyond Neptune’s orbit has 10 times the mass of the asteroid Main Belt. This buys only about three more doubling times. Massive imports from the even more distant cloud of billions of comets surrounding our solar system are not practicable with today’s science, as the journey times become decades to centuries. So we will be up against hard limits a few centuries from now.

On the way to hitting the 1/8th limit, a post-scarcity society will face ethical choices. Is any protection due to these (presumably) dead worlds? What places should be set aside as wilderness, or as common heritage? Are the millions of small asteroids worthy of being protected wilderness? What about the largest asteroid, such as Ceres, which may be the only survivor of the first phase of planet formation in the Solar System? Then there’s the largest mountain and volcano in the Solar System, Olympus Mons, or its largest valley, the Valles Marineris, both on Mars. Should these places be preserved in near-pristine condition? Saturn’s rings contain just enough water to re-fill Mars’ primeval ocean. Would it be moral to strip-mine those rings until they are all gone? If we find life on Mars, should we preserve it? Would destroying an entire tree of life, even a small one, be a greater tragedy than causing the extinction of one species? Carl Sagan once wrote, “If there is life on Mars, I believe we should do nothing with Mars. Mars then belongs to the Martians, even if the Martians are only microbes.”  Because not everyone agrees, it is an ethical question.

It does not take much of an imaginative leap to see that the 1/8th principle is just an extreme example of something that applies to the Earth too. We have been using exponentially more of Earth’s resources of all kinds for at least 200 years. Until recently the idea of exhausting those resources seemed as remote as exhausting those of the Solar System to most of us. Our work gives a clear warning that escaping to space is not escaping exhaustion.

We came to our conclusions by thinking about asteroid mining, not as an abstract idea but as a concrete question. How much is there out there to be mined? It is practical? What happens once we start mining? The people working on space mining had not put in the numbers for the whole enterprise. They were concerned only about the details of how to do it and how to make a profit. The bigger picture approach also matters, by helping us anticipate problems and deal with them ahead of time. And meanwhile, this offers a lesson for the Earth-bound.

Martin Elvis is an Astrophysicist at the Harvard-Smithsonian Center for Astrophysics. He is the author of Asteroids: How Love, Fear, and Greed Will Determine Our Future in Space.

Disclaimer: The ideas expressed in this article reflect the author’s views and not necessarily the views of The Big Q. 

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