How to flood the entire lunar surfaces?

Question

Given that the surface gravity on the Moon is a fraction of Earth and there is virtually zero atmospheric pressure but I still want to wet our beloved moon with whatever liquid that is known to science. It can be liquid nitrogen or a cocktail of acids etc, assuming the present day tech level and the only handwavium is awarded to transportation of the liquid and nothing else how can we cover the entire (at least 95% of lunar surfaces) with liquid solution so that the shallowest depth is about 1 m for at least 1 year? (I'm trying to figure out how the new tug of war between a planet and its moon will play out.)

Clarifications:

• Money isn't an issue.
• Foams are not allowed.
• It can be any kind of liquid not necessary water

Answer 1

How much we need?

Rounding down Moon to a roughly flat ball with the average distance to the planetoid center and then making a hollow sphere to the highest elevation via math gives us the estimated volume of liquid we need to fill. So:

$V=\frac{4 \pi}{3}(R_{peak}^3-R_{sea}^3)$

Taking 1737.4 km for moon sea level, the highest point goes 10.786 km above that. This gives a volume of:

$V=411722695.8934 \text{ km³}$

That only fills to just about the top of the highest mountain, demanding 5 km coverage, brings it to a generous $V=604296935.9922 \text{ km³}$, so your preferred solution is somewhere between those two extremes.

In other words: it's a huge lot of liquid. If that would be water with a density of $\rho=1 \frac{\text t}{\text m^3}$, it would weigh ${4.1 \choose 6.0} \times 10^{16}\text t$. That is still much less than the weight of the moon (which ranges in the $10^{19}\text t$ area), but it is a considerable fraction: you would add about $\frac {1 \to 2} {1000}$ of the mass of the moon itself if you take water.

Adding that much weight would have a substantial effect on the Moon-Earth system though, resulting in a decaying orbit and crash on a long term timescale, but that would be a better question for Randall Munroe, who might dedicate that question of world destruction a blog entry. So I skip on that and go to what our ocean has to endure.

Environmental Problems...

Obviously, water will freeze due to being exposed to an environment of at coldest $26 \text K$ on the surface of the moon and $3 \text K$ at the surface to outer space. To complicate things, fluids start to evaporate much earlier (as much as close to $0 \text K$ for Hydrogen) due to reduced pressure. And above that, the Moon's surface gets very very close to $400 \text K$ in the sun, because rock is a very very bad thermal conductor.

In the end, pouring all the water onto moon will just help in creating a jagged ice crust that more resembles an uneroded Europa than a liquid. Why uneroded? Europa encounters daily tidal forces, just like Tethys, which keep the inner water layers of the planetoid in a liquid state due to the extreme magnetic fields of the gas giants they rotate around. Earth can't grant that field - and both these snowballs have an outer crust of ice, not a fully liquid ocean, so the water solution is kind of out.

What to take?

So we got to take something that doesn't boil away, gets blown off the moon by the solar wind and doesn't freeze to solid by exposure to the temperatures. But here is the problem: there are not too many substances that are in liquid state in an environment facing to the $3 \text K$ and near vacuum environment of outer space... actually I could come up only one single material that actually is a liquid in an environment close to that: Helium boils at $4.22 \text K$ and remains liquid till very very close to absolute 0. it would weigh 0.125 tons per m³... but that is at 1 Atmosphere pressure, while we got a 0 atmosphere out at the upper edge of our ocean, which again... makes our precious ocean boil away due to reduced boiling point.

Hydrogen (which boils at $20 \text K$) is not an option, as it freezes at $14 \text K$.

End of the line

No, you can't create a fluid ocean on moon, as it has neither a protective magnetic field (which would keep the sun wind away to allow the creation of an atmosphere and thus any pressure at all), nor is there a liquid that would be fluid in the whole $3 \to 24 \text K$ temperature range that we can expect on coldest point, and especially there is no substance that is liquid for the whole $3 \to 400 \text K$ range that we have to deal with on the day side. This does ignore the temperature averaging effect of the fluid though, but still:

No Atmosphere = No oceans in fully fluid state.

Answer 2

If we are hand waving the transportation of the liquid, then the source is easy: Tethys.

Tethys' density of 980 kg/m$^3$ and spectroscopy of its surface indicates that it is almost pure water ice. And it weighs 6e20 kg, so plenty of water to go around. Assuming incompressible liquid water, it has enough payload to bury the moon under 16km of water. Even if you just slammed it into the moon, the probably has enough gravity to keep a good portion of that water. If you put it in orbit around the moon (note: do not attempt at home! gravitational effects on Earth-Moon system have not been validated!) you could break it off in chunks and throw it at the surface to liquidate the water without liquidating the moon itself.

Also, there are plenty of smaller ice moons or icy comets around to supply water for you. Also also of note, if you put that much water on the moon, a lot of it will evaporate due to low pressure and solar radiation. But only up to the partial pressure of water at current surface temperature. The result will be an atmosphere on the Moon, at least for a while until everything cools down and freezes.

Answer 3

Reading on Terraforming the Moon a while ago, it does seem to be marginally possible by repeatedly peppering the surface with comets until enough gasses had accumulated to create an atmosphere, which would then allow a liquid water hydrosphere to form. Obviously, this would not submerge the entire surface of the Moon under water (other answers have already calculated the vast amount of water required), but so long as you had accumulated enough gasses to build an atmosphere which could hold liquid ocean and allow people to walk unprotected on the surface, it seem plausible that such an atmosphere could remain for over 10,000 years.

The low gravity means the Lunar atmosphere extends for hundreds of kilometres, resulting in spectacular cloud formations

While not long on a geological time scale, this is still twice the length of recorded history on Earth, so sufficient time to allow a civilization to grow and prosper.

Of course, any really smart people who were doing this would also arrange for an artificial magnetic field and probably seal the entire Moon in a vast "bubble" of artificial diamond to keep the air in, but brute force engineering could supply the solution.

Answer 4

Doesn't have to be water? Great!

Water is stupid anyway, boils off, totally. For a short time you get residual ice and snow, and earth has a ring system, but you don't want to sell space postcards, do you?

So, to business: What you need is a liquid without vapour pressure. Ionic liquids. They're cheap, you can get them at a few hundred euros per liter nowadays. And I'll give you a real good discount for any order of more than 200 cubic kilometres.

Getting the feedstock for my lunar factories might be a bit tricky in the beginning. But I'm sure we can work something out with my friends who collect spent comets and stray asteroids to get all the necessary carbon and fluorine.

I really hope your bank will be up to it. Delivery is immediately stopped when monthly advance payments are interrupted.

As a plus, I guarantee without additional cost a minimal amount of foaming for at least six months. Can be extended to 12 month for a modest 25% surcharge, in advance.

Answer 5

Self-replicating nanobots that consume the regolith and burried ice deposits and produce nanoparticles that don’t adhere to each other, so it behaves as liquid at our scale.

The hard part is providing energy. If the biofilm is on the surface of the rock and below the growing layer of heavy fluid, the fluid should transmit sunlight. Large particles are usually black (think petrolium) or some opaque pigment. To make it clear the particles are engineered to support surface phonons in the manner of plexiglas.

The pool of heavy oil will Enhance the metabolism of the biofilm, protecting against damaging UV and passing the frequencies that can be used for power, blocking solar wind particles, and carying off heat. It will also serve as a medium to move different resources around as deposits of needed atoms will be found in different places.

It might be designed as an ocean of nanotech manufacuring bots! That’s why it was done. Once booted up to produce a biofilm and pool filling some lowland or crater depression, you can introduce instructions to produce a larger variety of nanobots which manufacture goods of all kinds.

Why let it fill the whole moon, overflowing the original basins and forming ever larger seas? Because it increases capacity and connects geologically diverse regions where different materials can be found automatically.

Perhaps the civilization that produced it falls or “ascends” and leaves it to go feral. A few million years later you have something like Code of the Lifemaker but based on nanotechnology it is more indistinguishable from the kind of ecosystem we are familiar with.

Answer 6

You're going to need a lot more than current tech (it would be a huge industrial undertaking to make the factories to make the stuff to make the liquid) to 'generate' any type of liquid, even if you handwavium away the transport problem.

If you merely want to move existing liquids, and you're handwaviuming from Earth to the Moon (simplest case), your only possible viable option is seawater (well, perhaps if you were willing to kill everyone on Earth by stealing their freshwater... you'd have two options) - but that won't stay liquid for long.

Given enough handwavium transport, we could coat the Moon in cometary-ice, I suppose.

We don't have the tech to keep any of the waters (salt or fresh) from freezing, unless we handwavium a space industry (I hope we get to transport it and all of the materials needed with handwavium, too). It might be possible to set up enough mirrors (using existing technical ideas) to heat the dark-side of the moon - but that's a lot of material to make and place, and to run in order to keep all of this water liquid. ie: Again with making huge industries, and probably 10s of thousands of people (maybe we could get away with just under 10k people... but I doubt it).

Covering such a huge amount of the Moon's surface is going to be problematic. The lunar high point is 1938 meters higher than Everest. Granted we won't have to go that high (let's go with 8.848 km high), and surface area is 38 million km2 is 3.36224 × 10^14 m2 of liquid.

That's a substantial number.

Unless my math is wrong, all of the seawater on Earth only amounts to 1.386 x 10^12 m2, a couple of orders of magnitude less than you would need.

Answer 7

Oh, that's easy.

Melt it.

Place giant mirrors in orbit of the moon and have them reflect and concentrate the sun onto the moon's surface. You are going to want to heat it slowly and evenly. Too much heat too quickly or heat applied to locally and you'll cause vaporization and/or stress fractures.

I'll add the math later tonight, but I'm sure it'll cost trillions of dollars.