In September 2023, Martin Elvis and colleagues at the Smithsonian Astrophysical Observatory published an estimate in the journal Frontiers in Space Technologies suggesting that even assuming 1 billion tons of water exist at the Moon’s poles, a city of about 1 million people would exhaust that water in roughly 100 years. The figure assumes a water recycling rate of 98%, on par with the ISS; if the rate drops to 94%, the time to depletion shrinks to 40 years, and some observational data suggest the actual amount of water may be only about 1/30th of 1 billion tons. On the 5channel Science News+ board, discussion split between doubts about whether a million-person city is even necessary in the first place, and arguments that gravity and effects on the human body pose more serious problems than water.
You Can’t Build a Million-Person City on the Moon: What an Estimate Showing Depletion in 100 Years — Even With 1 Billion Tons of Water — Really Means
Key points of this article
What happened: Even assuming 1 billion tons of water exist at the Moon’s poles, building a lunar city of about 1 million people would deplete that water in roughly 100 years.
Source: xenospectrum.com / Read the original article here
Oxygen can be obtained almost inexhaustibly from lunar soil,
but who knew hydrogen would be the bottleneck.
— with robots doing the work, 10,000 people would be plenty.
Where does that million-person figure even come from?
There aren't that many resources to be gained from advancing into the Moon or Mars anyway,
and it's unclear what economic structure would make it viable.
don't believe it.
Re: #10 even in this best-case paper, 100 years is the limit
Since even aliens with advanced science would have water problems, it's confirmed that if humans go out into space, they'd face the same conditions as on Earth.
*Even if aliens built structures hidden from human eyes, without water resources they'd have to either haul water frequently or bring it all at once with a large ship — which raises the risk of them being spotted by telescopes.
>>What makes the constraints even tighter is the 1-billion-ton assumption itself. More detailed recent orbital observation data suggest the actual amount of water may be as low as 34 million tons. Applying that more realistic figure — roughly 1/30th of the original estimate — means a million-person city's water would run out in just a few years. Rather than building a city, the resources would be exhausted in the early stages of construction.
If you actually built a million-person city, you'd have to keep firing off mass drivers nonstop just to keep it supplied.
Reading the article the other way around, though — it's saying a village-scale settlement of about 1,000 people isn't impossible?
So if all 1,000 of those people met every single condition, it might eventually open the door to expanding further into space?
That's a horrifying thought.
Because of the Sun's lifespan, we've only got about 300 million more years we can stay on Earth
we'll have to emigrate eventually.
Since water diffuses into the air, wouldn't buildings need to be sealed airtight?
you could bring the Moon's surface pressure up to 1 atmosphere.
Since lunar gravity is 1/6 G, the troposphere would end up around 60 km thick.
Once atmospheric pressure hits 1 atm, water could exist there too.
Oxygen could be made by electrolyzing the regolith, since it's silicon dioxide.
Venus doesn't have water, but Mars does — so melt Mars's ice, ship it to the Moon,
and just build an ocean there.
I don't think kids could grow up normally in the Moon's low gravity
and it's a health issue for adults too
You could conceivably haul water in from asteroids or wherever, but there's nothing you can do about gravity
If you're going to generate artificial gravity via centrifugal force anyway, it'd be far easier to just do that in orbit instead of on the lunar surface.
If we insist on flesh-and-blood humans, we could ship over just the genes after the initial development, or transmit the genetic data and synthesize it there.
so an unsustainable lunar society hobbled by a hydrogen shortage is arguably within acceptable limits.
Eventually we'll probably start crashing ice comets and asteroids onto the far side of the Moon one after another to get water resources.
Back in middle school I read an old book from the library called 'The Blazing Ice Planet.'
Wouldn't it be great if a planet like that just slammed straight into the Moon?
Are these guys stupid or something?
Zeon can keep fighting for another 10 years. (Gundam reference)
It'd be more efficient to redesign it
into something suited for space.
Just send AI robots to do the settling.
Large-scale water supply from other celestial bodies to the Moon is more like centuries to millennia out.
So, for the short term at least, it might work out somehow.
Background and key points of this discussion
This estimate is based on a paper published in 2023 by Martin Elvis and colleagues, and the constraints on lunar water resources themselves aren’t a new observation. What matters isn’t just the “total amount of water” but the “recycling rate” — whether the 98% water recycling rate achieved on the ISS can be maintained across a sprawling lunar living space is the biggest source of uncertainty. It’s easy to overlook that even a slight drop in the recycling rate cuts the time to depletion by more than half. The thread also noted that the 1-billion-ton assumption itself may be off by a factor of roughly 30 according to recent observations, underscoring how much the conclusion depends on the starting assumptions. Discussion in the thread split between skepticism about whether a million-person city is even necessary in scale, and pointers toward other constraints — like gravity and effects on the human body — being more serious, highlighting that water isn’t the only barrier to lunar settlement.
*This article is excerpted and summarized from the 5channel (Science News+) thread “[Space Development] You Can’t Build a Million-Person City on the Moon: What an Estimate Showing Depletion in 100 Years — Even With 1 Billion Tons of Water — Really Means.”
