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.
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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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