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Space: Farming on Mars will be a lot harder than ‘The Martian’ made it seem

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https://www.sciencenews.org/article/mars-farming-harder-martian-regolith-soil

Science News said:
In the film The Martian, astronaut Mark Watney (played by Matt Damon) survives being stranded on the Red Planet by farming potatoes in Martian dirt fertilized with feces.

Future Mars astronauts could grow crops in dirt to avoid solely relying on resupply missions, and to grow a greater amount and variety of food than with hydroponics alone (SN: 11/4/11). But new lab experiments suggest that growing food on the Red Planet will be a lot more complicated than simply planting crops with poop (SN: 9/22/15).

Researchers planted lettuce and the weed Arabidopsis thaliana in three kinds of fake Mars dirt. Two were made from materials mined in Hawaii or the Mojave Desert that look like dirt on Mars. To mimic the makeup of the Martian surface even more closely, the third was made from scratch using volcanic rock, clays, salts and other chemical ingredients that NASA’s Curiosity rover has seen on the Red Planet (SN: 1/31/19). While both lettuce and A. thaliana survived in the Marslike natural soils, neither could grow in the synthetic dirt, researchers report in the upcoming Jan. 15 Icarus.

“It’s not surprising at all that as you get [dirt] that’s more and more accurate, closer to Mars, that it gets harder and harder for plants to grow in it,” says planetary scientist Kevin Cannon of the Colorado School of Mines in Golden, Colo., who helped make the synthetic Mars dirt but wasn’t involved in the new study.

...

Palmer’s team suspected that the problem with the synthetic Mars dirt was its high pH, which was about 9.5. The two natural soils had pH levels around 7. When the researchers treated the synthetic dirt with sulfuric acid to lower the pH to 7.2, transplanted seedlings survived an extra week but ultimately died.

The team also ran up against another problem: The original synthetic dirt recipe did not include calcium perchlorate, a toxic salt that recent observations suggest make up to about 2 percent of the Martian surface. When Palmer’s team added it at concentrations similar to those seen on Mars, neither lettuce nor A. thaliana grew at all in the dirt.

“The perchlorate is a major problem” for Martian farming, says Edward Guinan, an astrobiologist at Villanova University in Pennsylvania who was not involved in the work. But calcium perchlorate may not have to be a showstopper. “There are bacteria on Earth that enjoy perchlorates as a food,” Guinan says. As the microbes eat the salt, they give off oxygen. If these bacteria were taken from Earth to Mars to munch on perchlorates in Martian dirt, Guinan imagines that the organisms could not only get rid of a toxic component of the dirt, but perhaps also help produce breathable oxygen for astronauts.

What’s more, the exact treatment required to make Martian dirt farmable may vary, depending on where astronauts make their homestead. “It probably depends where you land, what the geology and chemistry of the soil is going to be,” Guinan says.

...
 

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Whaaaaaaaat movies lied to me??? But yeah I know enough about plants to know that this shit is complicated. Why not just do hydroponics? Or would that take too much water? Is it cheaper to ship up dirt (or whatever you want to put the plants in) than water?
 

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I suspect hydroponics would be the way to go at the start, on a small scale? So many barriers to ever setting up permanent bases on Mars...

As for shipping soil there, that would be prohibitively expensive and hard. Better to figure out how to treat the local soil, probably? Water will have to be found & mined there too.
 
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Roxxsmom

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Hydroponics, or a lot of processing of Martian dirt to make it more palatable to plants. It's not surprising that Earth dirt is far more suited, since it's been supporting plants for hundreds of millions of years.

Consider how long, though, it took for plant life to even get established on land in our own planet's history! I imagine there was probably a "watershed" time when the balance of bacteria, nutrients, moisture etc. finally reached a point where those proto plants could successfully grow away from bodies of water. Yes, photosynthesis ultimately uses CO2 and water, but plants also need an assortment of minerals and fixed nitrogen (the latter will also be absent on Mars).

I suppose another thing to look at would be GM plants to be more tolerant of the conditions in Martian soil. They are doing that already to get crops that can grown under less-than-optimal soil conditions here on Earth. For instance, if you can transplant pickleweed genes into wheat, maybe you could get a strain of wheat that thrives in saltier soil.

The question is whether or not there are some plants, or maybe other organisms (like some extremophilic archaea), here on Earth with genes that allow them to live in soil with those calcium perchlorates and a very alkaline pH etc., and if that would give food plants the ability to grow in Martian soil. It's also possible they could engineer some kind of succession, where they start with very tough plants that are simply inedible weeds, but they condition the soil so it can support more useful plants.
 

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I love The Martian but I'd read up a little about perchlorate toxicity to make me think the movie glossed over that complication far too easily. It makes me wonder if Mars, rather than becoming another world to house humans, may better serve to show how we should cherish our own planet.
 
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Chris P

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Assuming Earth and Mars had similar origins and similar makeup originally, I think the biggest difference is the huge amount of water we have here, which has provided tons of weathering over the billions of years. The newer, unweathered fake Mars soil might not simply have had enough time to be transformed by the action of water and later the microbes and oxygen explosion that makes Earth soil palatable to plants. Just an hypothesis, anyway.
 

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Why didn't they just GM the crops in Interstellar? Why did they only have corn.

Anyways, Earth is the way it is because of billions of years of symbiosis and working together. (Cyano?)bacteria made oxygen as a waste product and put O2 in the atmosphere, things evolved to breath oxygen, trees figured out land is cool, things evolved to eat dead trees (I think the lignen specifically?), it just keeps going and going. Just thinking about the biomes in our GI tract and how they're unique to every individual shows how every species relies on countless other species to do the most basic things. None of those are on Mars. Gotta send up a bunch of Aerogardens, I guess. Or spacebuckets. Elon needs his space weed.