Between 2014-2016, red Romaine lettuce was grown on the International Space Station (ISS).
Scientists “sowed” surface sterilized seeds in a plant growth room nicknamed “Veggie”, equipped with LED lighting and an irrigation system. Lettuce was grown for 33 to 56 days.
Once collected, the crew members ate some leaves and frozen the rest for chemical and biological analysis on earth.
Now, the results have arrived. And Gioia Massa, a scientist at the Life Sciences Project at NASA’s Kennedy Space Center, told FoodNavigator that the results promise a lot for future long-distance space missions.
Vertical agriculture in space?
“Veggie” is a closed system, which means that temperature, carbon dioxide and humidity data can be monitored.
This method, Gioia explained, is not unlike vertical agriculture. Otherwise known as plant factories, vertical farms are completely stacked and fully controlled environments used to produce food.
“Our growth techniques have many similarities to land-based vertical agriculture”,Gioia told FoodNavigator. “We work closely with the agricultural community in a controlled environment while we are developing hardware for the production of future space crops.”
NASA’s current Veggie system – built by Orbital Technologies Corporation – is not as sustainable as its future systems will become, predicted the life science project scientist, “But we are learning lessons from Veggie to understand which aspects of plant growth need to be monitored and controlled in future space crop production systems.”
Currently, the team is using a substrate with controlled release fertilizer mixed in it. However, in the future, Gioia suggested that any substrate should be reusable – “Or preferably, we won’t have a substrate.”
“Safe to Eat” Zero Gravity Lettuce
In order to compare space-grown lettuce with its conventional counterpart, scientists have grown control plants on Earth under the same conditions. Temperature, carbon dioxide and humidity data were recorded on the ISS and replicated in the Kennedy Space Center with a delay of 24-48 hours.
When frozen lettuce was analyzed on Earth, scientists discovered that it was largely similar in composition to the controls grown on Earth.
However, in some studies, but not all, the plant tissue grown in space tended to be richer than some elements, such as potassium, sodium, phosphorus, sulfur and zinc. Phenols, which are molecules with “proven antiviral, anticancer and anti-inflammatory activity”, have also been detected.
A biological analysis revealed that the 15 most abundant microbial genera on the leaves and 20 on the roots were similar for both plants grown on Earth and space ones. None of those detected are known to cause disease in humans.
“This study indicated that leafy vegetable crops can produce fresh, edible and safe foods to supplement the astronauts’ diet and provide basic data for the continuous operation of the plant units grown in Veggie on the ISS”, Noted the authors of the study.
A potential diet change for Mars
According to Gioia, fresh produce – such as lettuce grown in space – could help improve astronauts’ diets on longer missions.
Currently, astronauts have an “excellent processed and packaged food system,” he explained, which includes around 180 foods and “another couple of dozen” drinks and condiments.
However, while the food system is nutritious and of high quality, both vitamins and quality degrade over time. “This is not a concern for the ISS, where they regularly receive fresh food, but it is a concern for a mission to Mars [planned for the late 2020s], where it may be necessary to send food to the crew in advance. ”
The imminent Artemis-III missions, scheduled to land humans on the lunar south pole by 2025, are also classified as “long distance”.
“So we’re trying to grow fresh produce to supplement this packaged diet to provide the nutrition astronauts will need.”
Fresh produce can also help provide new textures and flavors for the crew, Gioia continued, and can help with “menu fatigue” by adding variety to the diet. “Growing plants can also provide psychological benefits to the crew” He added.
The scientist also suggested that growing plants may have an impact on life support needs, which could prove crucial for further exploration of space.
“Plants absorb the carbon dioxide that astronauts are breathing out and generate oxygen to breathe the crew. If we ever want to be self-sustainable in space colonization, the plants will be whole. “
Lettuce today, sweet potatoes tomorrow?
The team has used these same cultivation techniques for other green leaf crops successfully.
They are now working on developing suitable approaches to growing small fruits, such as tomatoes and sweet peppers, and starting ground research on herbs.
“At the moment, there is no way to cook anything on the ISS, so fresh salad crops and herbs that can be eaten without processing are top priority”, Gioia related this publication. “Microgreens are another active research area, as they can be very applicable to space flights.”
When crews have cooking skills, such as a microwave or oven, the team will examine vegetables that require “minimal processing”, such as potatoes or sweet potatoes.
“For longer term systems on a planetary surface, additional staple crops could be grown to help provide the diet, but things like wheat and soy require significant processing before consumption, so they are quite far away.
“This type of production would be suitable when we have an almost permanent base on the surface of the Moon or Mars, for example.”
Source: Frontiers in Plant Science
“Microbiological and nutritional analysis of lettuce crops grown on the International Space Station”
Published March 6, 2020
Authors: Christina L. M. Khodadad, Mary E. Hummerick, LaShelle E. Spencer, Anirudha R. Dixit, Jeffrey T. Richards, Matthew W. Romeyn, Trent M. Smith, Raymond M. Wheeler and Gioia D. Massa.