Over in his lab at Utah State University, Paul Kusuma, 26-year old PhD student from Florida, scrutinizes the progress of lettuce in its airy, LED lighted growth chamber. Kusuma conducts research for his mentor, Professor Bruce Bugbee, in a $15 million, five-year NASA-funded program for the Centre for the Utilization of Biological Engineering in Space (CUBES) that began in 2017. Astronauts need to eat. Space shuttles fly best and are cheapest with minimal weight. So, for the last three years, Kusuma studied plant and crop physiology in the College of Agriculture and Applied Sciences and tested conditions for growing plants on Mars.
Growing Food on Mars
Given the right conditions, you can grow plants on Mars. Earth’s atmosphere is 78% nitrogen with 0.04% carbon dioxide. In contrast, Mars has more than 95% carbon dioxide with 2.6% nitrogen. Mars has 100 times less nitrogen than Earth. And nitrogen is essential for plant growth. It gives plants its green color and fruit-bearing potential, among other items. Indeed on Earth, lightning bolts release nitrogen from the atmosphere sending it down to the plants in the rain as nitrates, no such luck on Mars.
“But that’s no problem.” Kusuma told me, “In a controlled environment on Mars, we would manipulate the atmosphere to become more Earth-like. Plants only need CO2 [carbon dioxide] for photosynthesis and some oxygen for respiration...”
The main shortfall is the rocky, meteorite-prone surface of Mars – its crushed-up rock with high iron content and chemical perchlorates – and its high doses of UV-radiation. Kusuma plans to circuit that issue by growing plants several meters underground in earth-like conditions.
“They will be nurtured,” Kusuma told me, “electronically under the soil through vertical farming.”
Plants would be laid out either on a wide surface, or stacked one above the other underground. They would be grown hydroponically, without soil and using mineral nutrient solutions in a water solvent. The last would include bacterial E12 supplements that are essential for vegans, since these astronauts are moored to a vegan diet. The space farms would be nurtured with LED lights.
How Far-red Light Stimulates Plant Growth
Kusuma’s focus is on LED far-red photon light. Light travels a spectrum from lightest blue to deepest red. The question then becomes which band in the electromagnetic spectrum grows space plants best: Is it violet, blue, green, yellow, orange or red? And which shade of any of these colors produces the best results?
Over the years, Professor Bugbee found that far-red photons – a band of radiation at the very edge of human vision – slanted leaves to shield plants from shade and developed large leaves to maximize radiation capture. Bugbee and his team were also interested in blue and UV effects on plant growth. Typically, these wavelengths shrink plants. If they did so, the researchers wanted to know by how much and whether light should be added. Anything or none at all? Studies in the 1990s found there was approximately a 50% increase in growth when a small fraction of blue was added to red (not far-red) LED light.
Paul Kusuma’s Experiment with Far-Red Light
This is one of Kusuma’s most recent experiments that he drafted in a peer-reviewed article scheduled for publication. As he told me:
We set-up some experiments where the total number of photons was kept constant (from 400 to 750 nanometers), but we added different amounts of far-red into the spectra (0, 10 20 and 50%). Sunlight contains about 18% far-red, so we were testing both above and below natural ratios. Additionally, we tested the effects at three different intensities: 100, 200 and 500 μmol of photons m-2 s-1. So with three intensities with 4 percentages of far-red we had a total of 12 small chambers.
Setting this up in the small growth chambers, we wanted to test these responses which required a small amount of electronics knowledge. We could dim or increase the intensity of the LEDs by changing the drive current flowing through them. We had to know at what point the LEDs would break from being overdriven and set them accordingly. This process took several months to solder, mount, dial-in and test the specific LED combinations, but eventually, we got all 12 chambers to where we wanted them.
Then we had to choose a crop to test, plant and begin the experiment.
We tested a few different species in this system now, but I will only talk about our results in lettuce (cv. Rex) here.
Results are still preliminary, but it generally appears that at low light intensities (a photon flux density of 100 μmol m-2 s-1), the far-red photon increases stem length in lettuce, which we do not want. But at higher intensities of light (500 μmol m-2 s-1), far-red can increase the leaf area without sacrificing increases in stem length.
Put another way, we found that the plants grown under high intensity with more far-red had a higher dry mass than those without far-red. This means that if we want more leafy green, we should increase far-red photons into the electric lights.
Space Food on Mars
Back in 2016, scientists from the International Potato Center in collaboration with NASA planted potatoes in soil from the Pampas de La Joya desert in Southern Peru, a dry, salty environment that contains the most Mars-like soils on Earth, according to NASA scientist Chris McKay.
Professor Bugbee stated that growing potatoes on Mars could actually work. But Kusuma believes this is a longer term goal. Plants like spinach, lettuce and other leafy greens will come first. These crops could provide vitamins and minerals to the astronauts while also supplying psychological benefits. Later down the line, scientists could try more calorie-dense foods like potatoes, sweet potatoes and rice. Grains, such as wheat, barley, buckwheat and so forth would be simple and superb – but that’s forgetting the problems of downstream processing and turning them into food. (How, for instance, do you build a mill on Mars, never mind its baking process!)
As for livestock, these may graze Mars sometime in the future. Kusuma asserted it would be the far far future.
“The basic idea that NASA put forward is ‘How do we get what we need to sustain life on Mars with what is available on Mars,’” Kusuma said. “Nearly everything has to be made on site because the real expense of going to space is in moving things there.”
In addition to the costs, distances between Earth and Mars also mean no quick deliveries of crucial supplies. And supplies can only arrive and depart in specific windows of time due to planetary orbits.
For that reason, some researchers on the CUBES team focus on ways to integrate pharmaceuticals into their research, perhaps by modifying fast-growing plants like lettuce that can provide acetaminophen, or inserting genes for acetaminophen or antibiotics into bacteria.
The flavour of Mars is peppery
“And what does the food on Mars taste like?” I asked him. Astronauts say food tastes bland when they’re in orbit, for example on board the International Space Ship (ISS). This is because fluids pool in the head in microgravity, blocking off nasal passages and smell is a huge component of taste.
Kusuma told me that astronauts on Mars, which has somewhat more gravity than ISS but less than Earth, can taste food that is spicy, since the sharpness circulates blood around their heads. So Mizuna lettuce with its peppery kick is a delightful treat.
“I still can’t believe that I’m doing this,” Kusuma reflected. “About three years ago, I was unsure if I even wanted to go to grad school and here I am working on this interesting project. I enjoy going into work every day as I feel like I am playing a large role in the final frontier.”
Paul Kusuma Image Source Credit: Utah State University
Featured Image Source Credit: NASA: Artist’s rendering, astronauts exploring Mars will build hydroponic growth labs where vegetables can be grown. These crops will provide the crew with added nutrition and variety Credit: NASA
