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I understand that this is an inherently ridiculous idea. Earth is covered in water already. But in our current reality, rich people on Earth pay for bottled water that's been shipped halfway around the world because it's considered somehow "better" than local water.

In a hypothetical future about a century from now, if there's a colony on Mars and the Earth is polluted, rich people on Earth might be interested in purchasing "clean," "pure" Martian water, which could be harvested from known water-ice sources on Mars, such as the Korolev Crater and the Martian north polar region.

Assume that interplanetary travel between Earth and Mars is common, including in large spacecraft that carry many people (I haven't decided yet how many is "many," but potentially hundreds). Technology would have progressed and improved, but there isn't any sort of human space travel going on other than between Earth and Mars and possibly some sort of scientific station on Earth's moon.

My question is about the technological feasibility and the logistics of this. How feasible would it be to transport enormous chunks of ice from the Martian surface to the surface of Earth?

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    $\begingroup$ We cannot discuss economics in a vaccum. At a minimum we'd need to know the supply and demand demand curves for Martian water. Basically how much water would be purchased at what price and how much water would be made available at each price. This is going to be dependent upon the specifics of the cultures and technology your world has as well as the amount of existing interplanetary infrastructure. We are also very strict about only asking one question per post. Asking is it economically viable is a different question than is it technologically feasible, or would it need processing. $\endgroup$ Commented Dec 28, 2025 at 21:55
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    $\begingroup$ I was editing this question to a form that makes sense on this site when I realized that what you're asking is irrelevant. I don't know whether to -1 or VTC, but your world is described to have common spaceflight between Earth and Mars... and yet you're asking if it's feasible to move ice from Mars to Earth? No offense, but... um... duh... yes. What this means is you haven't told us the actual problem you're trying to solve ("is it feasible" is a really bad question to ask here, we're not in the business of building the Real World). ... (*Continued*) $\endgroup$ Commented Dec 28, 2025 at 23:13
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    $\begingroup$ ... So, you have space flight... you can obviously freeze and contain water... what do you think is getting in the way of moving ice from Mars to Earth? Do everyting in your power to answer that question without using the word "feasible" or any synonym or similar word. For now I'll VTC:Needs More Focus and I'll happily retract when you clear this all up. $\endgroup$ Commented Dec 28, 2025 at 23:14
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    $\begingroup$ Water on mars would be... infinitely dirtier than water on earth purified using methods available in the early 20th century. $\endgroup$ Commented Dec 29, 2025 at 3:51
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    $\begingroup$ Are these 'rich people' living on 100% Mars water or is just being able to supply the Mars brand water bottles at their dinner parties? The difference between the logistics for each of these are likely a couple orders of magnitude in resources needed. $\endgroup$ Commented 2 days ago

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Since you have the ability to transport hundreds of humans between Earth and Mars it should relatively easy to transport seven thousand liters of water, ignoring the cost. Assuming an average human has a mass of 70kg a hundred humans will have a mass of 7,000kg which is the same mass that many liters of water. Transporting humans is more complicated than transporting blocks of ice or tanks of potentially frozen liquid. Your people will have at least the capability of transporting this much water per trip. If there's people willing to pay for the cost of transport, the technology in your world is sufficient to make it happen.

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    $\begingroup$ Agreed. Although you have to watchout for the scammers selling cheap Earth H20 as expensive Mars H2O. Very hard to tell the difference, especially if you add a little extra heavy water to match the exact Martian isotopic ratio. $\endgroup$ Commented 2 days ago
  • $\begingroup$ Yep, those space ships have to return to Earth to get their next set of passengers, so that part of the trip is "free". But, because of capitalism, the OP is going to have to share the ship with other goods coming from Mars, as well as people coming from Mars back to earth. And the cargo can occupy the same space as the once habitable areas, and then let the cargo be open to space for things that a lack of atmosphere and low temps doesn't damage, like ice. So the cooling of the ice is "free", too. $\endgroup$ Commented yesterday
  • $\begingroup$ "Free" except for the extraction cost, the cost of converting from human to liquid transport twice, and the fuel cost of transporting the extra mass. Just getting from orbit to orbit will cost 6km/s delta V. $\endgroup$ Commented yesterday
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Water will likely be used as a shielding material on interplanetary craft, with water tanks surrounding the areas where humans spend most of their time. These tanks will likely be tied into drinking and cooling systems, if only for emergency situations.

Rather than towing an ice chunk, if 'Mars' water becomes a desirable commodity, one way of bringing some to Earth would be to empty those tanks at Mars and then refill them with 'certified fresh Mars water'.

If the point is to actually get clean water instead of just being a status symbol, then this can be done by spending an amount of money so much less than that required to move water from Mars that it becomes insignificant in comparison.

Boiling water in a barrel and catching the steam to condense in another barrel is easily doable. Similarly desalination costs are rapidly dropping and, it is claimed, may be similar is cost to 'normal' municipal water in the near future.

To paraphrase a quote on a similar topic, if you have the technology and resources to terraform Mars, then it would still be much easier and cheaper to clean up Earth.

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A sample return mission from mars has been proposed and prepared, but not carried out. It would have cost about 11B$ for a payload of 0.5 kg of samples:

https://science.nasa.gov/mission/mars-sample-return/sample-retrieval-lander/

So it's possible and the baseline cost at we could do it today is 22B$ per liter. Probably a bit cheaper if we skimp on the container, the gross payload including packaging for that rocket is 5kg.

I'm assuming the water is right there ready to pick up in those craters.

How much cheaper you can do it in your story solely depends on the tech and economy available.

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