Being able to create colonies on other planets largely hinges on our ability to grow food in space. This is no easy task. Cold temperatures, high levels of radiation, and long night and day cycles are all large challenges that have to be overcome.
What's more, the cost of sending a pound (453 grams) of anything only as far as the low-Earth orbit is estimated to cost $10,000. This prohibitive cost means we simply can't build a sustainable colony out in space without it being able to grow its own supplies.
Thankfully, space programs including NASA, CNSA, DLR, and ESA are making strong progress in researching how to grow crops in space. Here are some of the ways that we can grow food for future extraterrestrial humans.
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1. With a special ingredient... urine?
Amongst the methods that have been tested for growing food in space, one is rather unconventional, to say the least. As the BBC reported in 2017, The DLR, Germany's space agency, has tested growing tomatoes in urine.
You might not know that most of the water onboard the International Space Station (ISS) is recycled astronaut urine. The DLR's Jens Hauslage thought, what if you could use the useful salts and minerals in astronaut urine to grow food?
By feeding bacteria into vats of urine, ammonia from the urine can be converted into nitrites and nitrate salts – a fertilizer. As Jens Hauslage's tests have shown, this allows for perfectly edible tomatoes to be grown.
2. With inflatable greenhouse and life support systems
Though lettuce and cabbage are already successfully grown aboard the ISS in small amounts, space colonies would need to do it en masse to be able to sustain themselves.
Led by Dr. Ray Wheeler, lead scientist in Kennedy Advanced Life Support Research, the Prototype Lunar/Mars Greenhouse project aims to find novel ways to grow vegetables in space.
One of these is the inflatable greenhouse, which grows food as well as plants that create oxygen for life support systems via a process called a bioregenerative life support system.
"We're working with a team of scientists, engineers and small businesses at the University of Arizona to develop a closed-loop system," Wheeler said in a NASA blog post. "The approach uses plants to scrub carbon dioxide while providing food and oxygen."
3. By choosing resilient space-friendly foods
With its space plant experiment, China showed us how quickly vegetation withers in the sub-zero temperatures of space.
It's important to choose the right food for space. We're not just talking about the right foods for an astronaut's or space colonist's diet — though this is important. The really important factor, to begin with, will be choosing plants that are resilient and can survive in space conditions.
Española peppers show great promise for space as they grow at high altitudes and grow relatively quickly. Ray Wheeler led studies on peppers that were sent up to the ISS.
"We were looking for varieties that don't grow too tall, and yet are very productive in the controlled environments that we would be using in space," he said.
4. By picking the right locations
Finding sufficient light for growing crops is one of the big challenges of growing crops in space. One issue on Mars, for example, is that it is periodically consumed by dust storms.
"Mars gets significant dust storms, which could block a lot of sunlight, and that must be considered," Wheeler said. "That's an issue, even if we're using a photovoltaic system."
As NASA points out, in 2007, a graduate student at the University of Colorado mapped the light intensity at the surface of Mars over the course of two Martian years.
The student's research showed that Mars receives 43 percent of the sunlight that we get on Earth due to its distance from the sun. Despite this, the Red Planet does have various areas at low altitudes that receive adequate light for plant growth. Sunlight levels will, therefore, be a big factor when deciding where to send the first humans to Mars.
5. Using those red and blue lights
If we successfully colonize Mars, what next? If intergalactic space travel one day becomes a possibility we would likely focus on planets in their solar system's habitable zones.
However, space exploration might take us to planets that are farther away from sunlight than the likes of Mars.
"An alternate approach to sunlight would be to use electric light sources. High intensities of efficient LED lights could be used to help push the plants hard," says Wheeler, NASA's space plant specialist.
"This is an area where NASA has been really right up on the edge of research and development," he says.
The Veggie plant growth system, which is currently used aboard the ISS, uses blue and red LED lights to artificially give plants the light they need to grow. In fact, using LED lights to grow plants is an idea that originated from a NASA-funded effort at the University of Wisconsin in the 1980s before the technology was patented with NASA-supported funds.
Where will space exploration take us? Only time will tell. One thing that's for sure though is that plant cultivation will have to go with us if we want to thrive and create sustainable colonies on other planets besides Earth.