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From NASA's Treasure Map for Water Ice on Mars:

"You wouldn't need a backhoe to dig up this ice. You could use a shovel," said the paper's lead author, Sylvain Piqueux from NASA's Jet Propulsion Laboratory in Pasadena, California. "We're continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land."

(emphasis by me)

I don't think you could dig up the subsurface ice itself either with a backhoe or with a shovel, unless it has already been broken up by a former event.

I think the buried ice will be hard as rock, likely with a considerable amount of regolith, so what will or could be the most cost-effective method to break up and collect this ice; cutting, blasting, drilling, chiseling, sawing or some other way of removing?

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    $\begingroup$ why do you think Sylvain Piqueux from JPL is incorrect? $\endgroup$
    – Erin Anne
    Oct 22, 2022 at 22:51
  • $\begingroup$ @ErinAnne Maybe Sylvain Piqueux meant that you could use a shovel to remove the regolith above the subsurface ice. $\endgroup$
    – Cornelis
    Oct 23, 2022 at 7:45
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    $\begingroup$ What I think is the actual paper, Widespread Shallow Water Ice on Mars at High and Mid Latitudes, seems to be concerned with depth and covering material. I agree that the quote probably is about exposing the ice, not collecting it. $\endgroup$
    – Erin Anne
    Oct 23, 2022 at 8:32

2 Answers 2

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We need to learn more about the nature of the water ice deposits at the site chosen for human exploration. It is likely that the ice is contaminated with a range of different materials such as perchlorates, chlorides, sulphates, silts, clays, sand, grit and rocks. Before water ice can be electrolysed it would likely need to be purified and that will depend on the nature and quantity of the contaminants.

It might well be easiest to melt the ice below the surface rodwell fashion using an underground heater and then pump the melt water out for further processing. Alternatively warmed and pressurized CO2 could be injected into a drill hole and water vapour could be collected by cooling the emergent gases or Pressure Swing Adsorption could be used to collect it. These methods could provide purified water suitable for electrolysis.

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  • $\begingroup$ Thank you, it would be interesting to see how these methods would work in practice, for instance it could be that much heat gets lost to the regolith above. $\endgroup$
    – Cornelis
    Oct 23, 2022 at 21:05
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    $\begingroup$ You might find some of the links here of interest: forum.nasaspaceflight.com/… $\endgroup$
    – Slarty
    Oct 23, 2022 at 22:13
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    $\begingroup$ Yes, some proper quantitative studies are required, although there is a fair amount of literature available for example ntrs.nasa.gov/api/citations/20205011353/downloads/… $\endgroup$
    – Slarty
    Oct 24, 2022 at 11:46
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Even though the paper Hardness and Yield Strength of CO2 Ice Under Martian Temperature Conditions concentrates on carbon dioxide ice it also compares the results with water ice. The strength properties of carbon dioxide ice are slightly lower than those for water ice.

The paper confirms that ice hardness increases with the reduction of temperature.

Concerning the question of what would be the most cost effective way to remove and collect subsurface [water] ice on Mars? The answer would be, ... it depends! It would depend on the temperature (analogous to hardness) of the ice, the thickness of the ice and how much ice would be removed in each pass of removal. It would also depend on whether there was the desire and means to thermally soften the ice before harvesting and if so, to what temperature should the ice be heated, but still remain solid, prior to harvesting. It would also depend on how much wastage of ice would be tolerated and how gentle or aggressive the process needed to be.

Aggressive blasting could send fragments of ice flying everywhere leading to highly fragmented ice, but also ice that could be lost and never utilized. A gentler blasting process where less explosive is used, on a wider blasting pattern, would result in less fragmentation and less fly-ice. The degree of fly-ice could be reduced by the use of blasting mats or covering the ice with additional finer regolith prior to blasting. By finer regolith I mean material that is reasonably uniform in size, no large rocks or boulders and can be easily moved and removed.

The benefits of cutting or sawing are the minimization of losses due to fragmentation of the ice. Chipping/Chiseling would essentially produce fragments that need to be shoveled or collected by a gathering arm loader. It could also be very tedious, but it has the advantage that explosives would not be required. It would be safer, but by not using explosives it removes the element of acquiring explosive and blasting caps and would be simpler. A rock breaker hammer could be used.

There is also the possibility of combining cutting/sawing with chipping. A saw could be used to cut the boundaries of a channel and the ice within could be chipped/chiseled out.

However, I would seriously consider melting the ice and capturing the sublimating vapors using a suction device at the point of melting and storing them into a tank. Mars has an atmosphere and a suction device would work on Mars. A heated pad could be applied to the surface of the ice or holes could be drilled into the ice and heat probes inserted into them.

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  • $\begingroup$ Thank you, I like the idea of a suction device, but wouldn't the heated pad have to be integrated into the suction device to prevent heat loss ? I imagine that within a transparent pad during several hours around noun the temperature could be well above the melting point,so maybe extra heating would not be needed. Since a backhoe would be usefull to remove the regolith it could also level the icy surface. $\endgroup$
    – Cornelis
    Oct 23, 2022 at 13:51
  • $\begingroup$ What about a Continuous Miner Machine with a large rotating steel drum equipped with tungsten carbide picks that scrape coal from a seam ? Could that be applicable for ice mining somehow ? $\endgroup$
    – Cornelis
    Oct 23, 2022 at 14:07
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    $\begingroup$ After I posted my answer & shut down my computer the thought came to me that some form of grinding could also be used to extract the ice. Either an adapted continuous miner or the type of machine that removes the top surface of sealed (bitumen based) roads when they need to be resurfaced. See pavement milling or cold planing. Caterpillar cold planers. $\endgroup$
    – Fred
    Oct 23, 2022 at 23:06
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    $\begingroup$ The other term used is asphalt milling. $\endgroup$
    – Fred
    Oct 23, 2022 at 23:16

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