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My son wants to replicate some experiments and try to grow plants in Martian soil for his A-level science project. I know NASA have managed to produce soil that mimics Martian soil, however I also know how expensive it is.

My question is, what is the closest proxy to real Martian soil that I can create using readily available supplies from builders merchants, garden suppliers, chemists, and supermarkets?

Many thanks in advance.

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    $\begingroup$ we either need a price range or what you consider the threshold for "closest proxy" to answer this. $\endgroup$ – John Jan 19 at 15:24
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    $\begingroup$ Unfortunately, the real martian soil is rather toxic, en.wikipedia.org/wiki/Martian_soil $\endgroup$ – Conelisinspace Jan 19 at 16:02
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    $\begingroup$ But, there's also mudstone, that you could pulverize. en.wikipedia.org/wiki/Mudstone#Mudstone_mineralogy_at_Mars $\endgroup$ – Conelisinspace Jan 19 at 16:20
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    $\begingroup$ FWIW apparently you can buy various types of Martian soil simulant for $25/kg from the University of Central Florida sciences.ucf.edu/class/exolithlab $\endgroup$ – djr Jan 19 at 21:34
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    $\begingroup$ Those of us who have seen the film are waiting for you to mention the missing ingredient... $\endgroup$ – RedSonja Jan 20 at 11:57
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the other posters are correct - true Martian soil contains perchlorates, high levels of iron, and can be highly toxic. What you want to look for is called "Mars Regolith Stimulant". There are a few websites that have recipes.

https://reprage.com/post/home-made-simulant-mars-dirt

The five most abundant ingredients, account for almost 90% of the dirt taken from Mars samples.

  • SiO2 - 49.5%
  • Fe2O3 - 17.9%
  • Al2O3 - 7.2%
  • MgO - 7.7%
  • CaO - 6.7%

That seems like a good starting point. If I pad those out to reach 100% and use the results as a weight ratio, it should make a decent first batch of home-made Martian soil. Luckily most of this stuff can be found in hardware and health food stores.

SiO2

Silicon dioxide, yeah sand. You can go budget and get a bag of propagation sand (it won’t be 100% silica). If you want a bit more precision you can hunt around for educational or scientific samples that contain less impurities. You can get 2.7 kilograms for about \$16

Fe2O3

Iron oxide, is red cement colouring and is often advertised as red oxide or similar. You can get 2.2 kilograms for about \$20

Al2O3

Aluminium oxide, is used as an abrasive. It gets stuck to sandpaper and is used in sandblasting. It was a bit difficult obtaining smaller amounts in Australia (places wanted to sell me 20kg bags). You can get 340 grams for about \$10.

MgO

Magnesium oxide, is a dietary supplement found in health food stores. You can get 225 grams for about \$10.

CaO

Calcium oxide, Now this one is tricky. I couldn’t easily buy calcium oxide. It seems that calcium oxide reacts with CO2 in the air and gets converted into calcium carbonate. But you can buy calcium carbonate (CaCO3) as a dietary supplement. This can then be turned into calcium oxide by ‘lime-burning’, just heat it up in a kiln to above 825°C. You can get 340 grams of calcium carbonate for about \$10

and others that lets you buy your own (I won't link to them because of advertising, but the Martian garden is one such site). I think you could get close with the above recipe.

In any scenario, I would strongly recommend supervising your child when they are working with the stimulant. It should be handled with gloves and a respirator mask. Ingestion is very dangerous, and it might not be the worst idea to check the number of your local poison control center. While this may seem like overkill, it would make a great section of your child's science project. "Methodology", "Safety", and "Standards & Practices" are all very important parts of working in a lab and in engineering.

Best of luck!

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    $\begingroup$ As well as getting the right materials, it might also be important to discuss how to prepare it. At a guess, the biggest challenge would be getting the particle sizes right. $\endgroup$ – djr Jan 19 at 21:26
  • $\begingroup$ The article above just says to mix... Who knows! $\endgroup$ – mothman Jan 20 at 6:45
  • $\begingroup$ Do you think this is fertile enough to grow plants with ? I think mudstone is much more fertile, because it contains a lot of clay minerals. mars.nasa.gov/resources/8194/… $\endgroup$ – Conelisinspace Jan 20 at 9:35
  • $\begingroup$ This answer is wrong. The listed oxides are the chemical composition of the soil, not the mineralogical composition (which is what you need). $\endgroup$ – Gimelist Feb 24 at 3:53
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https://en.wikipedia.org/wiki/Martian_regolith_simulant#MGS-1 has a link to a standard for Martian regolith that includes recipes. It will, though, not be trivial to replicate the grain size from the minerals. Silicate stuff is hard, one might need an expensive mill or grinder to produce it, or a friend who works at a stonecutter's workshop. Perchlorates are not included in the standard, yet, but maybe its healthier to leave that unimportant detail (slight sarkasm :-)) away.

Mind potential health risks !

Suggestion: maybe it would suffice for an A level project to visit a site where one could take away a basalt, grind it somewhere and sterilize it (heat it to >100°C for an hour or so).

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Just as there are many different rocks and soils on Earth, so there are many different rocks and soils on Mars. To reproduce a Martian soil, you need to bear two things in mind. Firstly it should have all the vital nutrients plants need to grow, and secondly it should have no component of biological origin. That rules out limestone for a start.

Your soil should contain nitrogen, phosphorous, potassium, magnesium, sulphur and calcium. A volcanic tuff would be the best way to obtain these materials from a non-biological source; volcanic soils are known to be very fertile. If you can't find tuff, basalt and granite will do. Both are found in UK in areas where there were once volcanoes, such as Snowdonia in Wales and in Edinburg and other parts of Scotland. Granite will give a more acidic soil than basalt.

Grind or pound your basalt into a fine powder. Do the same with your granite. If there are some wheat grain sized granules in your granite, it doesn't matter, natural soils have them too. You should prepare a number of pots with different proportions of the two main ingredients. A little silicon dioxide sand might be worth adding to some of your pots, there is plenty of it on Mars. Then sow your seeds and see what happens.

Different plants have different soil requirements, so you should try more than one species. The trickiest ingredient to obtain, and one of the most important, is nitrogen. several sources of nitrogen on Earth, for example lightning discharges and urine, are not available on Mars. I wonder if a sprinkling of potassium nitrate would count as cheating. It occurs as an evaporite on Earth, but I haven't heard that any has been found on Mars. See how well your plants can manage without it. Potassium nitrate (saltpetre) is available from chemists.

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    $\begingroup$ PS. The nitrogen problem could be overcome by growing a legume (pea family). Legumes are able to fix their own nitrogen, and leave behind an enriched soil. I suggest French beans, which are a bit like runner beans except that they don't climb. As with runner beans, you can eat the pods. $\endgroup$ – Michael Walsby Jan 20 at 8:20
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    $\begingroup$ The question was about Martian simulant, not potting soil. $\endgroup$ – user18607 Jan 22 at 14:09
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    $\begingroup$ The object of simulating Martian soil is to see how things would grow in it when the astronauts tried to supplement their rations. Ultimately it is desirable that a manned base should be as self-sufficient as possible. To simulate one of many possible Martian soils which has no need to grow anything is too easy for words. You could make it pure silicon dioxide sand! $\endgroup$ – Michael Walsby Jan 22 at 14:29

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