Plants in space
Plants are unsung heroes, essential for longer term deep-space exploration by crewed spacecraft
Plants are unsung heroes, essential for longer term deep-space exploration by crewed spacecraft
Plants have played a pivotal role in space exploration efforts and will be critical for future space travel. From humble beginnings of just a handful of seeds hitching a ride into orbit to sophisticated plant-cultivation systems on the International Space Station (ISS), space-based plant research has come a long way. Astrobotany is not only integral for long-term space travel endeavours, it has also significantly benefited our lives here on Earth.
15 years before Yuri Gagarin embarked on his historic first flight into space, a very different kind of pioneer made the trip. Scientists wanted to observe the effects of space on biological material, sending a handful of maize (corn) seeds into orbit before committing to anything more substantial. These little seeds were not only an important stepping stone to getting humans into space, but also marked the dawn of the astrobotany era.
Since then, countless plant varieties have made a similar trip, including spinach, broccoli, rice and lettuce. In 2019, China made history when it sprouted cotton plants in the Chang’e 4 lunar lander biosphere experiment. These little plants were the first to germinate on the Moon, though their success was short-lived when nighttime temperatures plummeted to -170 degrees Celsius (-274 degrees Fahrenheit), killing the young seedlings. But this was still a monumental achievement, highlighting the possibility of plant growth on other worlds, but also the fragility of such life and its great dependency on technology.
On the ISS, astronauts have been able to keep plants alive far longer than their lunar-based counterparts. Here plants are not only grown for research, but also ornamental purposes and even sustenance – even astronauts can’t get away from eating their greens! The ISS provides unique environmental conditions to conduct experiments to see how plant growth and behaviour change when exposed to microgravity.
Both plants and humans have to adapt to microgravity during their space voyages, though much to the surprise of scientists, it appears that plants are far quicker to adapt to the lack of gravity than humans. Their development doesn’t appear to be derailed by microgravity, and they still
“Growing plants on board adds a sense of nature, a sense of home and a sense of life to the ISS” Mike Hopkins
manage to orientate themselves correctly despite there being no clear ‘up’ or ‘down’ in space.
On Earth we know that plant roots grow down away from light and shoots grow up towards it. From these observations, scientists believed that plant development – specifically plant growth direction – was driven by both gravity and light. However, plants surprised scientists when their root growth away from light and shoot growth towards it were unaffected by the lack of gravity in space. This proved that light is the dominant driver of plant growth direction, not gravity. This revelation would not have been possible without experiments carried out in space.
Space-based research isn’t just beneficial for learning more about how our little green friends behave, it has also greatly influenced our lives here on Earth. In 1989, the NASA Clean Air Study found that certain plants were particularly good at ‘cleaning’ the air around them. These air-filtering plants rid the air of pollutants and toxins, which could not only help sustain a healthy environment for astronauts, but also benefit those of us who spend a lot of time indoors. Chemicals such as formaldehyde, benzene and ammonia can be released in small amounts by regular household products such as printing inks, varnishes, paper towels and plastics. While adverse health effects such as nausea and headaches depend on the level of exposure to such chemicals, certain houseplants can help limit this exposure by removing these pollutants from the air. Plants such as English ivy, variegated snake plants, peace lilies and spider plants are considered some of the best for their air-cleaning qualities. These results have greatly influenced the popularity of air-filtering houseplants to this day.
While plants are natural air and water purifiers, they cannot operate at the levels required to keep space environments safe for astronaut colonisation. Instead scientists are trying to understand how plants remove such toxins from their environment to come up with new technologies that can keep space-based environments habitable. At the moment sophisticated equipment helps scrub the air of pollutants, but is not self-sufficient and requires replacement of parts during supply
“These plants are a connection to Earth”
Mike Hopkins
missions. While this is fine for current research missions, it will become harder to resupply those that venture further from Earth and for longer periods of time.
For longer term missions, sophisticated bioregenerative support systems are needed.
These will support life by providing oxygen and removing carbon dioxide from the air, purifying water and providing food. Such systems require a good relationship between plants and technology, as plants can help make the environment habitable through air and water purification and food supply, but they need the right technology, such as light supply, to enable them to grow. These closedsystem ecosystems are being tested in Earth-based research facilities such as Biosphere 2 in Arizona and BIOS-3 in Russia to assess how such systems could maintain and support life in space.
Another benefit of growing plants in space is a rather simple one: sustenance. According to NASA, stored food represents the largest consumable mass – apart from rocket fuel – for human spaceflight. To sustain long-duration exploration missions, astronauts need to be able to grow more of their food, as raising livestock in space would be impractical and a logistical nightmare.
On the ISS there are a variety of plant-growth experiments designed to study in-orbit plant growth and performance. In 2015, Expedition 44 crew members enjoyed the fruits of their labour when they harvested their ‘Outredgeous’ red romaine lettuce, and were permitted to eat half of their bounty. The other half was packaged up to return to Earth for further experimentation. This marked the first-ever crop to be grown and eaten in space, a giant step forward in space-based foodproduction research.
This important research not only aids future space exploration efforts, but also has implications for our future here on Earth. “If we can discover how to sustainably grow healthy, robust and consistent crop yields in a place as inhospitable to life as Mars, we can apply these discoveries to transform how we grow food here on Earth,” says Gil Cauthorn, a PhD student at the University