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How Flowering Plants Are Helping NASA on Its Journey to Mars

Plant problems are a great learning experience.
Image: NASA

Astronauts aren't the only life forms on board the International Space Station right now. A crop of Zinnia flowers are beginning to bloom in spite of a recent mold outbreak. NASA astronaut Scott Kelly tweeted a picture of the first Zinnia blossom yesterday.

The Zinnias are part of a plant growth experiment known as Veggie. The plants are housed in a special plant growth chamber, first installed in the station's Columbus module in 2014. So far, two crops of red romaine lettuce have successfully grown in the chamber, with astronauts sampling some of the leafy greens last year.


Veggie has simple goals: to provide astronauts with fresh food and to help boost morale. Growing plants has enormous psychological benefits. "The astronauts seem to really enjoy caring for the plants," said Dr. Gioia Massa, NASA's science team lead for Veggie. "And they really love the chamber's purple light. I see lots of tweets and photos about the light." Experiments like Veggie bring crews together and help provide a connection to Earth, something they miss while being in space.

Also, fresh fruits and vegetables are a rarity in space simply because they have to be shipped up on one of the resupply missions. With those happening only a few times per year, things like salads are a special treat. Veggie aims to change that.

NASA astronaut Steve Swanson of Expedition 39 with the LED lights of the Veggie plant growth system. Image: NASA

Before astronauts can enjoy a steady supply of salads, they have to tackle the issue of growing plants in microgravity. The Veggie experiments are not the first set of plants (or flowers for that matter) to ever grow in space. The first flowers grew in 1984 on the Salyut 7 space station, followed by wheat stalks on Muir, and zucchini seeds (also a flowering plant) sprouted on the ISS back in 2012. Veggie is the next phase in plant growth experiments and is designed to produce plants the crew can eat.

Leafy greens, like the red romaine selected for the first two iterations of Veggie are hearty plants and easier to grow than flowering plants. However, the first crop of lettuce faced some challenges. The first crop struggled with watering issues and several plants were lost due to drought-related stress. As a result, the next crop was monitored more closely and the majority of the plants thrived.


Mold Growth on the plants. Image: NASA

Water doesn't flow in space like it does here on Earth, so determining the best way to water the plants was a big hurdle. The plant growth chamber houses six plant pillows, and is outfitted with the seeds, nutrients, and water system. Two seeds are "planted" within each pillow, to ensure at least one of them will germinate. After about 7 days of growth, if two plants sprout the weaker plant is harvested, allowing the healthier plant to thrive in the pillow.

The plants receive the bulk of the water from a root mat underneath the pillows. Each pillow has a fabric bottom, so the plants can passively wick from the reservoir underneath. The astronauts can also water the pillows directly. Nutrients are absorbed from a controlled-released fertilizer also housed in the pillow.

According to Dr. Massa, the red lettuce takes about 28 days to grow, while the zinnias take about 60-80 days. The zinnias were not selected because they produce pretty flowers, but because they are a good precursor to tomato plants, which take up to 90 days to produce fruit. Ensuring the plants receive the proper amount of water for that long is a challenge in space.

Two weeks into the zinnia's growth cycle, the crew noticed an issue with the watering system. The plants were covered in extra water which led to mold growth. An unexpected spacewalk led to delayed treatment for the mold, resulting in the loss of three plants. Ground crews suggested turning on the plant chamber's fans which dried out the plants too much. With the next scheduled watering a few days away, astronaut Scott Kelly was concerned they would not make it.


He voiced his concerns over having to follow a predetermined schedule instead of using his judgement and deciding how best to water the plants. "You know, I think if we're going to Mars, and we're growing stuff, we (meaning the astronauts) would be responsible for deciding when stuff needs water," he told the ground team.

Equipped with a one page Zinnia care guide and his intuition, Kelly was given control of the experiment. Thanks to some TLC, the Zinnias have rebounded from the mold outbreak and started to bloom.

Yes, there are other life forms in space! Scott KellyJanuary 16, 2016

"The plants haven't grown perfectly," said Dr. Massa."We've had some watering issues. But, I think we have gained a lot from this, and we are learning more about plants and fluids and also how better to operate between ground and station."

The lessons learned in this Veggie experiment are helping both astronauts and ground crews prepare for the trip to Mars and future deep space missions. The next round of crops are heading to the space station soon aboard SpaceX's CRS-8 mission. Dubbed Veg-03, this round of experiments will feature two different sets of Chinese cabbage, and another round of red romaine lettuce. Then in 2018, NASA will launch a set of dwarf tomato plants and we could see crews eat the first space salads.