How Mold on Space Station Flowers is Helping Get Us to Mars
When Scott Kelly tweeted a picture of moldy leaves on the current crop of zinnia flowers aboard the International Space Station, it could have looked like the science was doomed. In fact, science was blooming stronger than ever. What may seem like a failure in systems is actually an exceptional opportunity for scientists back on Earth to better understand how plants grow in microgravity, and for astronauts to practice doing what they’ll be tasked with on a deep space mission: autonomous gardening.
“While the plants haven’t grown perfectly,” said Dr. Gioia Massa, NASA science team lead for Veggie, “I think we have gained a lot from this, and we are learning both more about plants and fluids and also how better to operate between ground and station. Regardless of final flowering outcome we will have gained a lot.”
The next crop on the docket was a batch of zinnia flowers, but they weren’t selected for their beauty. They were chosen because they can help scientists understand how plants flower and grow in microgravity.
“The zinnia plant is very different from lettuce”, said Trent Smith, Veggie project manager. “It is more sensitive to environmental parameters and light characteristics. It has a longer growth duration between 60 and 80 days. Thus, it is a more difficult plant to grow, and allowing it to flower, along with the longer growth duration, makes it a good precursor to a tomato plant.”
Just more than two weeks into their growth period, though, NASA astronaut Kjell Lindgren noted that water was seeping out of some of the wicks – the white flaps that contain the seeds and stick out of the tops of the plant pillows. The water partially engulfed three of the plants. Within 10 days, scientists noted guttation on the leaves of some of the plants. Guttation is when internal pressure builds and forces excess water out of the tips of the leaves. It occurs when a plant is experiencing high humidity. Additionally, the zinnia leaves started to bend down and curl drastically. This condition, called epinasty, can indicate flooding in the roots. The anomalies all pointed to inhibited airflow in the plant growth facility that, when coupled with the excess water, could lead to big problems for the crop.
“After observing the guttation and more significant amounts of free water we decided to see about toggling the Veggie fan from low to high,” said Smith. “We had evidence indicating reduced airflow through the internal Veggie facility volume, and needed to toggle the fan to high to dry things out.”
“When you have high humidity and wet surfaces,” he said, “leaves start dying, and become prime real estate for mold to grow.”
The mold issue had Smith out of bed and the Veggie team on the phone by 4 a.m. Within four hours, new procedures were written and communicated to NASA astronaut Scott Kelly, who took over care of the zinnias after Lindgren returned to Earth on Dec. 18. Kelly donned a dust mask as a safety measure, and cut away the affected, moldy plant tissue, which was then stowed in the minus eighty degree laboratory freezer (MELFI) so it could be returned to Earth and studied. The plant surfaces and plant pillow surfaces were sanitized with cleaning wipes, and the fans continued at a high speed in hopes of keeping the Veggie chamber dried out and mold growth abated.
By Christmas Eve, though, Kelly called down to the ground support team to report new problems with the plants. It seemed the high fan speed was drying out the crop too much, and Kelly said he thought they needed more water. He was told, though, that the next scheduled watering was not until Dec. 27.
“I think that would be too late,” Kelly told the ground team. “You know, I think if we’re going to Mars, and we were growing stuff, we would be responsible for deciding when the stuff needed water. Kind of like in my backyard, I look at it and say ‘Oh, maybe I should water the grass today.’ I think this is how this should be handled.”
News of the mold didn’t dampen Smith’s Christmas spirit, though.
“We’d been planning on figuring out how to garden autonomously and his request was just perfect,” Smith said. “Christmas Eve 2015 was our gift!”