While NASA could send up space tubes full of pureed meats and heavily processed vegetables, in the long run the goal is to make the ISS more self-sufficient. Future missions there and to other planets will require crews to produce some of their own food. Gardening in space? As it happens, it's possible but it must be done in a completely new way.
Anytime a plant undergoes stress of any kind, whether it's from drought, insect invasion, organic bacteria or pollution it changes the way the plant grows. Plants react to these environmental stressors and part of the point of growing food on the ISS is to find out how and hopefully minimize the stress and increase the yield of plants grown for food.
To begin with, plants on the ISS are not just placed in a pot of dirt while the crew hopes for the best. The project is as high tech as farming can get. Seeds are encased in special "pillows" with a rich soil mixture and a watering mechanism. They are then placed under LED lights, in a color combination of red, green and blue. Because of the zero gravity environment on the space station, plants cannot always sprout upwards as they would on Earth, so the pillow system keeps everything going in the right direction. The seeds are activated and in about a month, plants can be harvested. Expedition 39 astronaut Steve Swanson grew the first veggie pillows in May 2014, but those plants were not used for food, but instead picked, packaged and sent back to Earth to be evaluated by NASA researchers.
In July of this year, astronaut Scott Kelly activated a seed pillow of a lettuce variety called "Outredgeous" and those plants grew well and were harvested 33 days later. The crew of the ISS used half of the lettuce for meals, while freezing the other half to be brought back to Earth. This crop will contain the first plants grown in space to be eaten by astronauts, so it's a major milestone in farming and raising plants for human consumption. The cost of shipping food to the ISS has been estimated at approximately $21,000 per kilogram, so the more food that can be grown in space, the lower the costs will be on future missions.
In addition to red lettuce, the plant growth unit aboard the ISS, aptly named Veggie, will also grow tomatoes and blueberries, both high in antioxidants which researchers hope can give crew members some protection against the large amounts of radiation the are exposed to in space.
Check out the video below for more information on farming in deep space.