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Water is required for human explorers of Mars and it is also widely expected to be used to synthesize methane rocket fuel for the return trip (by combining the water with CO2 and energy to create methane and oxygen). Water could also be pumped into the lining or roof of a habitation to provide radiation shielding.

But how do you mine subsurface water that is frozen solid without heavy equipment?

The only think I can think of would be a drill with a head that emits heat or microwaves to melt the water and then it can be pumped to the surface and purified and processed. I'm not sure how practical that is. Would it make the ground unstable? Would you have to move the drill head frequently as each drill site gets exhausted?

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    $\begingroup$ I think not much water can be pumped this way because the heat or microwaves will not get very far from the drill so the pumping would have to be done within the same bore. So indeed you would have to move the drill head frequently. Maybe it would be more practical to use ice deposits. space.stackexchange.com/questions/25562/… $\endgroup$ – Cornelisinspace Oct 23 '19 at 13:04
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    $\begingroup$ You pump hot water down (or even better hot supercritical CO2) and a larger volume of cooler water back up (what you pumped down, plus ice melt). In the process you excavate a cavern under the ice, and you do need to take care to make sure it doesn't break through to the surface. $\endgroup$ – Steve Linton Oct 23 '19 at 13:35
  • $\begingroup$ Before mining water, it should be known where to find the water, location, depth, concentration. $\endgroup$ – Uwe Oct 23 '19 at 17:07
  • $\begingroup$ Surface ice distribution: en.m.wikipedia.org/wiki/Water_on_Mars#/media/… $\endgroup$ – Ags1 Oct 23 '19 at 17:37
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There are multiple designs for rovers and robots which are designed to pick up regolith from the surface and transport it for water extraction. For example, in this video, a rover is shown which has dual drum-excavators and is picking up the surface material in the simulated martian environment.

For such a rover to work, the water would need to be rather close to the surface and present in the form of ice or slightly damp regolith. After scraping the surface, the mining robot would deposit it's collected regolith into some sort of processing facility, which could then heat up the regolith and separate out the water.

For drilling or deep mining activities specific to Mars, I couldn't find any specific proposals. Seriously considering in-situ fuel manufacturing on Mars is a rather new topic, and, despite some re-engineering requirements, there's no reason conventional mining techniques wouldn't work on Mars as the do on Earth. Humans have a lot of experience getting things out of the ground and I don't think there would be any fundamental differences that prevent traditional mining techniques from being used on Mars.

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  • $\begingroup$ For ice in the surface layer the landing site would have to be relatively near to the poles. But I don't think I've seen a plan to put people so far north or south. Hence my thinking there would need to be drilling not mining. $\endgroup$ – Ags1 Oct 23 '19 at 17:35
  • $\begingroup$ We have to take some care heating the regolith. As noted here nitrates have been identified on Mars through heating the regolith, driving off nitrogen oxides. This "side reaction" and maybe others involving volatile matter could impurity the water. $\endgroup$ – Oscar Lanzi Oct 24 '19 at 0:35
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Making a drill rig mobile is easy; it simply gets mounted on a tracked or wheeled platform. Mineral exploration companies & water borers have used truck mounted drill rigs for decades. The technology can be adapted for use on other celestial bodies.

As to ground stability issues, this would potentially be a major issue if drilling sub horizontal holes beneath and overhang or into a sub-vertical rock face. Drilling vertical of sub-vertical holes into the ground generally would not present many issues. It would however, depends on the diameter of the drill hole, closeness of holes to each other and the nature of the ground: competent, loose rubble, sand, etc.

What may be issues are:

  • Jamming of the drill stem, if drilling through loose material.
  • Inappropriate drill & drill bit for the ground. An auger with a rotary drill would be more appropriate for loose material such as soil or sand. A button type bit with a rotary percussion drill would be appropriate for hard rock or frozen ground.

How the water would be mined will be dictated by the geology containing the water: sand, soil, porous sandstone (if it exists) and the thickness of the water bearing material.

Other approach that could be used is to use a surface scraping device, similar to earth moving scrapers used is come civil and mining application on Earth. The device in the video link in the answer by @dragongeek is a different form of scraping device.

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