Could astronauts grow plants in soil?

NASA has sent a lot of strange stuff into space. It sent gold-plated music albums and photos on the Voyager 1 and 2 space probes. It sent pieces of Kitty Hawk, the legendary Wright brothers' airplane, on Apollo 11. It sent a cargo tag, dug up at the historic Jamestown Settlement, on a space shuttle. And last month, it used a rocket to send dirt.

Well, soil actually. That's the mix of ground minerals, sand, organic matter and nutrients needed to grow food. Thirty-six vials of soil will be kept at the International Space Station (ISS). The ISS has been orbiting 254 miles above Earth for 20 years. After 30 days, the soils will be frozen until they can be sent home Dec. 29.

"We're trying to understand how the microorganisms in soils react in a microgravity environment," Morgan Irons says. (Microgravity means very low gravity. Despite what a lot of people may think, there is some gravity in space.)

Irons is a soil scientist at Cornell University in Ithaca, New York. Some of the soil at the ISS is hers. She dug it up from an organic farm plot on campus. Another soil sample is man-made from a waste product called biochar; and a third soil comes from Germany.

When her portion of soil returns to its home planet, Irons will study it to see whether anything about it has changed from its time in space. Will it still form the clumps that mean it has the right structure to help seeds grow? Will it contain the same amounts and types of bacteria and fungi as when it left Earth?

"Bacteria and fungi are so important for soil health and how plants (can get) the nutrients they need," Irons explains.

NASA has already experimented with growing plants in space hydroponically - in water without soil. Astronauts have experimented with growing them in clay "pillows" and in a special kind of gel. But this is the first time research is being done on whether they could be grown with natural soil taken from our own environments.

Irons said this is important for a lot of reasons: It can help us better understand how to keep soil healthy on Earth. It can help us look for soil on other space bodies that might still contain microbes. And it can help us figure out how we might "revitalize" the soil on Mars, where NASA aims to send astronauts in the 2030s.

"That goes into what people in the space industry call 'in situ resource utilization,' " Irons said. That is, "how can you use the resources you have on site, rather than, say, hauling up soil" from Earth.

Mars' surface is made up of a rocky material called regolith. The nutrients it contains aren't in the right form to be used by plants. Irons knows from experimenting with a similar kind of dirt that it turns hard like concrete when you add water. (So, no, the potatoes Matt Damon's character grows in the movie "The Martian" wouldn't work in real life.)

But "if we can figure out what microorganisms we need to introduce to regolith, and what plants could survive in such a harsh environment," Irons says, maybe we can figure out how to grow crops on the Red Planet.

Who's ready to be the first Martian farmer?

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