EPISODE 2: MUSHROOMS ON MARS
PLANT GROWTH SYSTEMS
Plant growth systems on the International Space Station (ISS) are critical to understanding how plants can be grown in microgravity environments and their potential to support long-duration space missions. These systems are carefully designed to provide plants with the essential elements they need to grow—light, water, air, and nutrients—while overcoming the unique challenges presented by space conditions, particularly the absence of gravity.
Here’s an expanded look at the primary plant growth systems used on the ISS, how they function, and their significance for space agriculture.
1. Veggie Plant Growth System (Veggie)
The Veggie Plant Growth System is one of the most prominent platforms for growing plants on the ISS. It is designed to be a relatively simple, low-power system that provides a space-friendly environment for plant growth.
Key Features:
- LED Lighting: Veggie uses red, blue, and green LED lights to stimulate plant growth. Red and blue lights are particularly important for photosynthesis, as they provide the wavelengths plants need to convert light into energy. Green light is less essential for plant growth but is included to make the plants appear more natural to the astronauts, which can have a psychological benefit.
- Open-Air Design: Unlike more controlled environments, Veggie operates in the open air of the ISS cabin, meaning the plants grow under the same atmospheric conditions as the astronauts. This includes carbon dioxide levels and temperature, making the system simpler in terms of air management.
- Plant Pillows: One of the most innovative aspects of Veggie is the use of "plant pillows," small pouches containing a substrate, fertilizers, and seeds. The substrate is typically made of a porous material like clay or fabric that holds water and nutrients for the plants. Plant pillows help anchor the plants in place, as the absence of gravity means they cannot rely on soil to hold them steady. The pillows also help prevent water from floating away in microgravity.
- Watering System: Watering in space is tricky because water behaves differently in microgravity. The Veggie system uses a wick-based watering method. The plant pillows contain wicks that draw water from a reservoir, ensuring the plants have a consistent water supply without the need for gravity-based watering.
- Crops Grown in Veggie: Veggie has successfully grown crops like red romaine lettuce, zinnias, mustard greens, radishes, and mizuna. These experiments have shown that leafy greens and other fast-growing plants can thrive in microgravity.
Significance:
Veggie is important because it offers a relatively simple way to grow plants in space with minimal intervention. It also allows astronauts to interact directly with the plants, including harvesting and consuming the crops, which is vital for understanding the psychological benefits of growing food in space.
2. Advanced Plant Habitat (APH)
The Advanced Plant Habitat (APH) is the most sophisticated plant growth system currently on the ISS. It is a fully automated system designed to precisely control the growing environment for a wide range of plant species.
Key Features:
- Fully Controlled Environment: Unlike Veggie, the APH is a closed system where environmental factors like temperature, humidity, oxygen, and carbon dioxide levels are tightly controlled. This makes the APH an ideal platform for scientific experiments that require precise control over the growing conditions.
- LED Lighting with Full Spectrum: The APH uses a broader spectrum of LED lights, providing more flexibility for experiments that study how different wavelengths of light affect plant growth. The light intensity and duration can be adjusted to simulate day and night cycles, as well as different environments on other planets.
- Root Modules and Hydroponics: The APH includes multiple plant-growing modules, some of which use hydroponics (growing plants in nutrient-rich water without soil). This allows for the study of various plant growth methods in microgravity.
- Airflow and Gas Exchange: The APH has an advanced ventilation system that ensures plants receive the necessary gas exchange for photosynthesis and respiration. This system also helps prevent the buildup of ethylene, a plant hormone that can accumulate in the closed environment of space and negatively affect plant growth.
- Cameras and Sensors: The APH is equipped with cameras and a wide array of sensors to monitor plant health in real-time. Researchers on Earth can observe the growth of the plants, adjusting conditions remotely based on sensor data.
- Automation: One of the APH’s defining features is its high level of automation. Watering, nutrient delivery, and environmental controls can all be managed automatically, reducing the need for astronaut intervention and ensuring consistency in experiments.
Crops Grown in APH:
In the APH, researchers have successfully grown crops like wheat, radishes, and peppers. The APH is particularly useful for growing more complex plants, such as fruit-bearing plants, which require more sophisticated environmental control.
Significance:
The APH is crucial for conducting long-term experiments that study how plants respond to the space environment over multiple generations. It is a key platform for advancing our understanding of plant biology in space, particularly for developing crops that can provide food and oxygen for future long-duration missions, such as a journey to Mars or establishing a lunar base.
3. Biomass Production System (BPS)
The Biomass Production System (BPS) was an earlier experiment system designed to study plant growth on the ISS. Although it is no longer in active use, the BPS was an important precursor to the Veggie and APH systems.
Key Features:
- Controlled Growth Chambers: The BPS featured four independent plant growth chambers, each with its own environmental controls. This allowed for multiple experiments to run simultaneously under different conditions.
- Hydroponic Growth: Like the APH, the BPS used hydroponics to grow plants, studying how nutrient delivery systems work in microgravity.
- Sensors and Cameras: The BPS had cameras and sensors to monitor plant growth, focusing on real-time data transmission back to Earth for analysis.
Crops Grown in BPS:
Plants such as wheat, mustard greens, and Arabidopsis were grown in the BPS, which helped scientists gain insights into how microgravity affects early plant development and seed production.
Significance:
Though retired, the BPS laid the groundwork for more advanced systems like Veggie and APH. It provided early data on how plants might adapt to the space environment and how to design future systems for space agriculture.
4. LADA Greenhouse
LADA Greenhouse was a Russian plant growth system used on the ISS for experiments conducted by both Russian and American scientists.
Key Features:
Modular Design: The LADA system included a small, compact growing chamber that could be easily set up and monitored by astronauts. It was designed to be a simple, practical tool for growing plants in space.
Soil and Hydroponic Growth: LADA allowed for both soil-based and hydroponic growth experiments. It also featured a built-in watering system to ensure that plants received the correct amount of water in microgravity.
Ventilation System: LADA was equipped with a fan-driven air exchange system to provide plants with oxygen and remove excess CO2.
Crops Grown in LADA:
The LADA Greenhouse was used to grow crops such as peas, wheat, and lettuce. These experiments focused on understanding how plants grow in space and how to create efficient, small-scale agricultural systems for future missions.
Significance:
LADA played a key role in expanding international cooperation on space agriculture, as it was used by both NASA and the Russian space program to explore plant growth in microgravity.
5. Bioculture System
The Bioculture System is designed more for studying plant biology at the cellular level, focusing on plant cell cultures rather than full-grown plants.
Key Features:
Tissue Cultures: This system is designed to grow plant cells and tissues in microgravity, rather than whole plants. It provides insights into how cells behave in the space environment, including how they grow, divide, and respond to various stresses.
Sterile Environment: The Bioculture System provides a highly sterile environment for growing plant tissues, minimizing contamination risks and allowing researchers to focus on the cellular responses of plants to space conditions.
Remote Monitoring: Like other systems, the Bioculture System can be monitored remotely, allowing scientists on Earth to control the experiment and gather data without needing constant astronaut intervention.
Significance:
The Bioculture System is important for understanding the fundamental biology of plants at the cellular level, helping scientists learn how space conditions affect plant growth and development at the molecular level. This research informs future efforts to grow crops in space by ensuring that plant cells can function properly under space conditions.
Why These Systems Matter for Space Exploration
1. Supporting Long-Duration Missions: As we prepare for missions to Mars or establishing permanent bases on the Moon, the ability to grow food in space is crucial. These plant growth systems provide valuable data on how plants respond to microgravity, helping us develop sustainable agricultural practices that can reduce reliance on resupply missions from Earth.
2. Providing Oxygen and Removing CO2: Plants not only provide food but also play a vital role in recycling carbon dioxide into oxygen, which is essential for maintaining life support systems in space habitats.
3. Understanding Plant Behavior in Space: Each of these systems allows scientists to study different aspects of plant growth, from seed germination to fruit production and cellular responses. This research is key to developing crops that can thrive in space and on other planets.
4. Psychological Benefits for Astronauts: Growing plants in space isn’t just about food; it also has psychological benefits for astronauts. The act of gardening and seeing something grow in the sterile environment of space can provide a sense of normalcy, connection to Earth, and stress relief during long missions.
In conclusion, the plant growth systems on the ISS—like Veggie, APH, BPS, LADA, and the Bioculture System—are critical tools for advancing space agriculture. They help us understand how to grow crops in space and lay the foundation for future sustainable food production on the Moon, Mars, and beyond.