[♩ INTRO ] If we ever want to get to the point where we’re living it up in space colonies, then we’ve got a few big hurdles to overcome.

One of the big ones is figuring out what we’re going to eat. After all, we can’t live off prepacked freeze-dried food forever.

And calling in a several thousand kilogram takeout order to Mars isn’t exactly cheap either. So since the 1980’s, scientists have been studying how to grow plants in space, with the hope that one day we could grow them on a moon or even a Martian colony. But despite what certain movies might suggest, growing plants on another planet, or even somewhere closer to home, is trickier than you might imagine.

If we can crack the space-botany nut, future astronauts could benefit not just from a consistent food supply, but all sorts of plant-y goodness. Plants could also supply materials like fibers or beneficial chemicals. They might also circulate air or recycle water.

Or they could just be there to bring a bit of brightness and cheer to a pretty gray and machine-filled environment. I mean, look how many houseplants we all bought during the pandemic. One of the first plants astronauts managed to grow in space is Arabidopsis, a cousin to cabbages and radishes and part of the mustard plant family.

It’s a favorite model for study in the plant world because its relatively small genome and fast life cycle make it easy to work with. Arabidopsis was first grown in space in 1982 onboard the Russian Space Station. But NASA astronauts onboard the International Space Station have grown a whole host of other food since then, using their vegetable production system, dubbed Veggie.

Their safe-to-eat bounty has included Chinese cabbage, red romaine lettuce, mizuna mustard plants, and a mini form of bok choy. NASA also has another, fully automated version of Veggie onboard called The Advanced Plant Habitat. It uses sensors, cameras, lights and water and gas reserves that can monitor and control watering, temperature and oxygen and carbon dioxide levels inside its enclosed chamber automatically.

Using the Advanced Plant Habitat, astronauts have been able to grow dwarf wheat and, in 2021, edible peppers. All those growing experiments have been really important, because they’ve told scientists a lot about how plants grow in the conditions of space. Take something like gravity for example.

The ISS experiences microgravity thanks to its state of free fall. The Moon has one sixth of Earth’s gravity, and Mars has a bit more, but still only around 62% of Earth’s. So one of the first things researchers wanted to find out is whether plant roots still grow down when they don’t have the cue of gravity to guide them.

Turns out, plants seem to do just fine using strong light as a guide instead, with shoots growing up towards the light and roots away from it. But the lack of gravity can wreak other kinds of havoc on plants. Low gravity means that water behaves weirdly around plant roots.

In microgravity, it forms bubbles, which can surround the roots. And as you know if you’ve ever over-watered a houseplant, being too wet is bad for them. That’s why plants on the ISS grow in little pillows of clay, where the gaps in the clay trap just enough water and a little bit of air so that the roots can absorb the H2O without being waterlogged.

Now, growing plants onboard a high tech space station is one thing, but growing them on the surface of the moon or a planet is another. It wasn’t until 2019 that cotton seeds aboard a canister on China’s Chang’e-4 lander sprouted on the far side of the Moon. As well as the cotton seeds, this thermos-sized canister housed potatoes, canola, yeast, fruit fly eggs and the old favorite, arabidopsis.

The idea was these organisms would form their own mini biosphere – with the plants breathing out oxygen and taking in carbon dioxide made by the fruit flies and the yeast keeping the CO2 and O2 levels in check. The canister itself was supplied with temperature controls and a system that watered the plants when told to by ground control. Of all the seeds, we only know for sure that the cotton sprouted, and even then their life was pretty short.

A breakdown in the biosphere’s temperature control exposed them to the -190 degree Celsius lunar night. Researchers did still learn something from the super short experiment, which is that plants, at least cotton seeds, can sprout in the harsh conditions on the Moon. See, although the space station is technically in space it’s only about 400 kilometers away from Earth and still a pretty controlled environment, shielded from the extreme temperatures and cosmic radiation on the moon.

So, before landing the canister on the moon it was really hard to simulate the true conditions of space. And although the experiment didn’t go according to plan, in that researchers never got a chance to see if the organisms could work together in a self-sustaining mini biosphere learning what went wrong could help scientists build more resilient plant environments in the future. In addition to putting plants in an environment that suits them, researchers also need to investigate how to make the plants themselves more resilient to the harsh space environment.

One way to do that might be through genetic engineering. By tweaking the plants’ DNA, botanists could make them more resistant to the stress of spaceflight, make them grow better in low oxygen conditions, or make their roots shorter so they can fit more plants in a small space. We might even be able to go as far as to genetically engineer plants to grow in lunar or Martian soil.

Maybe part of the reason the cotton seeds were the things to sprout is because they were genetically engineered to be more hardy and insect resistant here on Earth. Scientists have already grown plants like tomatoes te the stuff you’d find on the Moon or Mars. Which might still be a long way from growing them on the actual planet, but it’s still one small step for humankind.

And could mean we’ll be munching on space veg on our way to the red planet in the future. Thanks for watching this episode of SciShow Space. We’d like to offer up a big old space salad as thanks to our patrons for helping us make it.

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