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How NASA and ISRO discovered water on the Moon (jatan.space)
172 points by uncertainquark 11 months ago | hide | past | favorite | 35 comments

This is potentially the most important discovery in planetary science to date. The reason, which is left until the end of this article, is that water can be electrolyzed to yield hydrolox propellant, i.e. rocket fuel.

Rocket fuel dominates logistics in space. The tyranny of the rocket equation is that it takes an exponential (literally exponential, not in the colloquial sense) amount of fuel for a linear increase in velocity. This is why it's so hard to go to Mars, and why we need to slingshot around Jupiter to go anywhere else.

A source of rocket fuel above Earth's gravity well would break the tyranny of the rocket equation, and serve as a stepping stone to other parts of the solar system where water is abundant (i.e. Ceres, Mars). Until we have nuclear or other exotic propulsion, water is the oil of space.

To paraphrase the lunar anthropic principle, if the universe had wanted humanity to become a spacefaring species, it would have given us a Moon, and it would have put water on it.

We're just scratching the surface of what these lunar water deposits mean.

I see it the other way around.

Earthers find it hard to kick the idea that hydrogen and hydrocarbons are fuels, but that is because oxygen is free on the surface of the Earth.

On Luna you might use that hydrogen to reduce hematite ore (found in commercial quantity by astronauts) to Iron and Oxygen. Oxygen is like 7/8 the mass of the fuel you need, you can make storage tanks, residential neighborhoods, whatever you want out of steel if you can find a small amount of carbon. You can recycle the hydrogen, it's not lost as it would be if you burned it.

Lunar oxygen mining to refuel something like the SpaceX Starship faces tough competition from Earth via the SpaceX Starship -- a 1990s study looked at 5 Earth to Mars mission scenarios with and without lunar materials and it wasn't clear you could win with lunar oxygen.

The moon is close in configuration space to the Earth but far away in phase space (including energy differences) NASA figured Apollo hardware could make it to Venus


because you can use resonances around the moon to get a kick away from the Earth as opposed to fighting the gravity well with a low-ISP rocket on the way up and down from La Luna (no, atmospheric reentry on Earth is not "a problem" but rather free delta-V and one hell of a preimage for your landing site)

A good main belt asteroid might be like Saudi Arabia but with the relative proportions of sand and hydrocarbons reversed. You would be looking at a solar 5km/sec mission unless we got lucky and found a medium rare asteroid in the "near earth" area.

Either way if you could build a chemical factory that can make things like Kapton, Mylar or sheet graphene it shouldn't be that hard to handle giant films to make a solar sail factory, install sunshades at L1, beam solar power to moon bases at night, etc.

Either more fuel or patience, and I think patience is going to win.

There are interplanetary 'highways' where you can spend barely any deltaV to go everywhere, provided you have patience.

Probes are already transiting Earth and Venus multiple time to get slingshots to outer solar system.

The ideal space base is a manufacturing hub in the asteroid belt. Where deltaV to go to anywhere else is ~0 and deltaV to launch stuff from base is also ~0. That's the only way to have star wars sized ship. Launching one from gravity well of the Earth or even Moon is just lunacy.

I know the guidelines on submission titles but this is a good example of how one (missing/removed) word completely changes the entire meaning.

Perhaps the "How" should be added back in?


Edit: The title has been changed. Originally, it was "NASA and ISRO discovered water on the Moon".

The "How" prefix was likely removed automatically during submission. dang has confirmed there is a list of suffixes and prefixes that this happens with, but it is not public what they are.

Edit: when I posted this the title was "NASA and ISRO discovered water on the Moon"

I'm fairly certain the word "quietly" is automatically removed from submission titles.

i.e. "Apple quietly drops case against X" => "Apple drops case against X"

However, I do think "quietly" provides extra context - it indicates Apple (in this fictitious scenario) did not issue an official statement on what they did or why; a 3rd party just happened to notice by reviewing public legal documents.

It provides context but also emphasizes a particular perspective, that the subject "should have" or maybe "would have been expected to" announce what they were doing more prominently.

The whole question of what is or is not news necessarily takes a certain perspective, though, so I guess this is always going to be a gray area.

It also implies a nefariousness that might not be appropriate.

That's true but given that HN (via dang and the rules) often states that it's supposed to be a more highbrow forum I think the subtleties of the title should be left to the author of the submission.

Yes, the the prefix was removed automatically even though my submission title was "The story of how NASA and ISRO discovered water on the Moon." Big difference indeed.

This is an interesting case where removing the word "How" makes the title more clickbaity rather than less!

In one case, it's an article about an amazing new discovery, in another case it's an explanation about the method of something we already know.

In this case, it makes a dramatic difference.

I’d like to correct the record here a bit. Although Clementine, the first spacecraft to sense water ice on the moon, was indeed funded by NASA (and the Ballistic Missile Defense Organization), it was in fact designed, built, and operated by my senior colleagues at the US Naval Research Laboratory. For some reason NRL rarely gets mentioned in this story even though it was our spacecraft!


> equivalent to at least 240,000 Olympic-sized swimming pools

For scale, the Earth has enough water to fill ~532 trillion pools.

Another perspective:

USA uses 322 billion gallons of water everyday. [1]

240,000 swimming pool contains 120 billion gallons.

USA would survive approx 8 Hrs on the moon.

[1] https://medium.com/ensia/america-uses-322-billion-gallons-of...

[Edit: Corrected. Thanks SamBam]

I think you swapped the numerator and the denominator. If the US uses more water than is on the moon every day, how would it survive 2.5 days?

(There's also some conversion problems because the article took the amount of water on the moon and estimated a number of swimming pools, and you've taken the number of swimming pools and estimated the amount of water. From the article, the moon has 600 billion kg of water, or 159 billion gallons.)

I wonder what the most efficient way to move bulk amounts of water out of earth's gravity well would be?

It's probably mostly like any bulk freight lifted to orbit/escape: you could pump it up space elevators, assuming you could get around the problems of making those; An orbital ring is more physically plausible but has a much higher initial outlay. Maybe you could accelerate a stream of it accurately enough that the resulting hail of ice would reach, say, an earth-moon l3/4 point slow enough to be continuously captured and processed.

One of the first futurists I read had a bunch of suggestions.

The most interesting was combining earth hydrogen with lunar oxygen freed up by reduction operations on moon regolith.

More pedestrian was having ships sell their surplus fuel to a transfer station in orbit. If your mission is completely nominal, you will have reaction mass that you no longer need. Better to leave it for the next guy. I'm not sure how you do that in a failsafe way, though. A burst line or a stuck valve could ruin everybody's day.

It might require aux tanks that can be removed. For longer missions that might be worth the complexity.

No need to do that - Ceres is a water world and you can haul it into cislunar space from there.

A LEO-altitude-to-GEO space elevator has been proposed as possible with near-current tech... so perhaps a railgun pop-up to catch an elevator?

If there is any amount of water, It could be life or life remains trapped on it. Maybe not based in cells, but other forms like viruses... Hum.

Is a really intriguing discovery. Maybe supporting the panspermia theory. Maybe leading to one of the biggest discoveries in our recent history. Maybe they could find several types of ice, if they came from different comets.

I hope that we could analyze this water before to burn it as fuel.

It would be nice if we could stop moving the goalposts to give credit to our favorite institutions. The Soviet probe Luna 24 in 1976 brought back samples that were found to be 0.1% water. "NASA and ISRO are the discoverers because they did the analysis without returning to earth" is such a cop-out.

What did the Soviets do that was special? Did the samples from the Apollo missions not show any water content?

Very little. What was there was dismissed as contamination, though a 2008 analysis showed small amounts of water locked inside pieces of volcanic glass inside the Apollo samples. The recent tremendous emphasis on the Chandrayaan-1 mission is motivated largely by the failure of Chandrayaan-2.

That's not right. The Chandrayaan 2 failure has nothing to do with the Chandrayaan 1 discoveries. The lander of Chandrayaan 2 failed but it was not tasked with a follow-up science of any of these water-related discoveries. That is the job of the Chandrayaan 2 orbiter.

[2019], [2009]

s/NASA and ISRO/Air Force/

Article can’t even get that part right....

Do you have any sources to back this up?

Well apparently I shouldn't have had the snark because even I couldn't get it right. Should have been US Navy, which built and operated the Clementine spacecraft which discovered large reservoirs of water on the moon. Follow-up missions by NASA and ISRO confirmed this with better instruments, but it was a military mission that made the initial discovery.

It's a bit of a contentious issue because loonies had trouble getting NASA interested in the Moon again, and NASA rejected without evidence the notion of cold trap volatiles. So they went around NASA and used defense money to get an early version of Lunar Prospector launched, which was the Clementine mission, and gave the evidence necessary to prove the value of the poles as potential sources of in-situ resources.

(I got all the details of this from a talk given by a retired Air Force general who was involved, so I mistakenly thought it was the Air Force that ran it. Looks like it was actually a research division within the Navy.)


Now I am worried about exploitation in the name of exploration by humans

Would it be so bad if the mining was on the far side of the moon?

It won't stop there.

Could be. One of the things I'm worried about is that I think space mining rhetoric has vastly underestimated the consequences of the dust, both on the moon and in the asteroid belt. It might take generations to scrape the far side of the moon, but the dust could be a problem within a few years.

I think it is possible to expand into space while maintaining nature.

The issue is doing it multilaterally, and in such a way that the proceeds are vaguely available to everyone. I don't mean space communism - consider Starlink: Currently it looks useful, but if they were to pollute space (e.g. astronomy) solely for the benefit of the US mainland I think you could easily argue it isn't justifiable internationally.

What kind of exploitation?

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