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Growing plants in space

Growing plants in space is a complex and complex task, presenting a number of unique challenges. However, research and experimentation in this field have progressed over the years, and efforts are underway to grow plants in space environments such as the International Space Station (ISS).


PART1 : The first space plant


Image 1: Close-up view of Arabidopsis thaliana grown as part of the "SPACE SEED" experiment. Source : NASA

the first plant to flower in space was Arabidopsis thaliana in 1982. This historic experiment was carried out on board the Soviet space station Salyut-7. Arabidopsis thaliana, also known as wall mustard, is considered the ideal model for plant biology due to its small size, short life cycle and ease of cultivation in the laboratory.

















The study carried out aboard Salyut-7 was significant, demonstrating that this plant could grow and produce viable seeds in weightlessness, although their morphology was slightly altered. This has paved the way for future plant-growing experiments in space, enabling scientists to better understand how plants react to the space environment and to envisage solutions for growing food in extraterrestrial conditions on future space missions.


PART 2 : A brief history


Willy Ley (1906-1969) was a German writer and scientist, best known for his work in the field of astronautics and space exploration. He played a major role in disseminating knowledge about space travel and helped popularize the idea of space conquest.


When it comes to plants in space, Willy Ley was one of the first to explore and promote the idea. He suggested that plants could play a crucial role in space missions by providing oxygen through photosynthesis and recycling the carbon dioxide exhaled by astronauts. He also pointed out that plants could help maintain a biological balance in space habitats by providing fresh food and helping to regulate humidity and air quality.


He was not directly involved in carrying out plant cultivation experiments in space, his ideas inspired future work and research in this field. As space technology progressed, plant cultivation experiments were carried out aboard space stations such as the ISS, where astronauts explored how plants behave in microgravity and extraterrestrial environments.


Research on Chlorella in the 1950s laid the foundations for the study of microorganisms and algae to support life and human activities in space. This work contributed to our understanding of life support systems in space, and paved the way for future experiments and studies on microorganisms and plants in extraterrestrial environments.


International Space Station: what experiments have been carried out?

Biology experiments carried out aboard the ISS have included the study of the effects of microgravity on plant growth, disease and vaccine research, the study of bacterial survival in space, and the analysis of tissue regeneration in salamanders.


Here are just a few examples of experiments carried out on plants:

  1. In the 1940s, the first research on algae in space was launched. These pioneering studies aimed to understand how algae behave and develop in extraterrestrial environments, particularly in microgravity. Algae were chosen for these early experiments because of their biological simplicity and their ability to carry out photosynthesis, a crucial process for oxygen production.

  2. In 1980, the Biomass Production System (BPS) experiment: carried out on board the Russian space station Mir, involved cultivating various plants, including wheat, beans and radishes, to study their growth and development in microgravity.

  3. In 2016, another milestone was reached when the first flower, a Zinnia, bloomed on board the ISS. This was a landmark event, as it demonstrated that plants more complex than vegetables could be successfully grown in space.

  4. From 2014 to 2016, crew members aboard the International Space Station (ISS) undertook the cultivation of lettuces. The resulting crops were brought back to Earth to be examined to determine their suitability for consumption. The findings of this study were released in March 2020, indicating that lettuces grown in space were as nutritious as their Earth-grown counterparts.

This exploit was made possible by the VEGGIE growth chamber. This growing facility, illustrated in a photo, comprises six compartments, each equipped with three essential sub-systems: an LED system emitting light at 660 nm (red) and 450 nm (blue), the two most efficient wavelengths for photosynthesis, an aeration system and a mat to fix the roots and provide them with the nutrients they need to develop. In 2016, the ISS experienced another historic moment when the first flower in space, a Zinnia, bloomed on board. These achievements represent significant advances in space gardening and open up new prospects for growing more varied and nutritious food in space, which is essential for long-duration space missions, including those planned for exploration of the Moon and Mars. These successes testify to the ongoing technological and scientific progress aimed at ensuring food autonomy for future astronauts on space missions.



Image 2: First flower to be grown in the Veggie cultivation system on the International Space Station. Source NASA.

Image 3: A photo of the VEG-01 or VEGGIE device. Source NASA



In April 2021, NASA astronaut Thomas Pesquet began his second space mission, heading for the International Space Station (ISS). One of his main objectives was to carry out various scientific experiments, one of which involved growing plants.


For this experiment, Thomas Pesquet used a method developed by NASA called "Plant Water Management" (PWM), based on the principle of hydroponics. Unlike traditional soil-based cultivation, hydroponics does not involve the use of soil, and requires less water and fertilizer. Plants are supplied with the minerals and nutrients essential for their growth. Thanks to good aeration, plants are able to germinate and grow directly in water, taking advantage of the capillary action phenomenon that works more effectively in microgravity than on Earth. As a result, plants grow three times faster than on our planet.


This innovative approach enables researchers to deepen their understanding of how plants react to the space environment, and also opens up promising prospects for agriculture in the space environment. These experiments are helping to expand scientific knowledge and prepare for future space missions involving extended stays, particularly with a view to more in-depth exploration of the Moon and Mars.


PART 3 : Space greenhouses


It was aboard the International Space Station (ISS) that plant studies really took off, thanks to the use of various growing structures, often referred to as "greenhouses".


Lada

In 2002, the Lada greenhouse was installed in the Russian module of the International Space Station (ISS) as part of a collaboration between the USA and Russia. This greenhouse included a control module and two plant development modules, enabling comparison of plant evolution in relation to different cultivation methods. The main objectives of the research carried out using this greenhouse were to ensure that "space crops are sufficiently healthy for human consumption" and to check that they do not cause internal contamination (by micro-organisms) within the ISS.


ABRS

The ABRS, or "Advanced Biological Research System", is equivalent to the American version of the Lada greenhouse, designed to conduct advanced experiments on plants, as well as micro-organisms and arthropods. It also includes two compartments for plant cultivation, each measuring 13 x 20 x 40 cm. The lighting parameters and atmospheric compositions inside these compartments are adjusted according to the specific needs of the experiments. Equipped with over 180 sensors, this system enables experiments to be remotely controlled from Earth via a computer operated by the ISS crew. The data collected is automatically transmitted back to Earth. The ABRS was designed from the outset to explore the possibilities of plant cultivation, while minimizing crew intervention.


VEGGIE

The VEGGIE equipment is distinguished by its simplicity but larger size, primarily designed for the production of plants for human consumption. Installed on the International Space Station (ISS) in April 2014, it is intended to remain there permanently. Its main difference from the equipment previously used for these studies lies in its open nature, allowing the plants to benefit from the space station environment. In fact, all experiments have confirmed that they pose no major health risk to astronauts.


Image 4: The VEGGIE greenhouse being prepared for installation on the ISS. Source Nasa













APH

The Advanced Plant Habitat (APH) has been deployed on board the ISS. This facility is specifically dedicated to research into the development of plants in the space environment, with the aim of preparing crews to grow part of their own food during space missions of (very) extended duration. It was in this facility that peppers were successfully grown in 2021. To pollinate the flowers, fans were activated, and the crew also intervened manually in the process.


Image 5: The Plant Habitat-04 experiment. Source Nasa












PART 4 : Plants on the Moon or Mars?


In a study published in the scientific journal Plos-One, researchers set out to examine the potential for plant germination in soils analogous to those found on the Moon or Mars. The aim of the study was exclusively to assess the nutritional quality of these soils or pseudo-soils. The researchers compared seed germination and plant growth in three different substrates. Each container contained 5 seeds associated with one of these three types of substrate, along with 25 g of demineralized water:

  1. 100 g of pseudo Martian soil (JSC-1A Mars Simulant), developed by NASA to imitate the composition of Martian soil, taken from a volcano in Hawaii.

  2. 100 g of terrestrial soil from the depths of the Rhine, 10 meters below the surface, extremely devoid of nutrients and organic matter.

  3. 50 g of lunar pseudo-soil, manufactured by NASA to simulate the characteristics of lunar soil, taken from a desert in Arizona.


The researchers wanted to determine the ability of plants to thrive in these particular environments, and the extent to which the different compositions could influence germination and plant growth.

The seeds were planted at a temperature of 20°C under humidity conditions of up to 65%. The seed varieties used were tomato, carrot, mustard, nettle, thistle, red fescue, lupine, birdsfoot trefoil, sweet clover, common vetch and rye...


At the end of the experiment, the Martian pseudo-soil showed the highest rate of germinated seeds, while the lunar soil showed the lowest germination rate. However, the authors note that the intrinsic quality of the seeds may also have played a role in the germination process. Leaf formation occurred successfully in both Martian and lunar pseudo-soils. Only three species (mustard, rye and watercress) reached the flowering stage, generating new seeds.


Some issues

Despite the progress made, growing plants in low-gravity environments such as the Moon and Mars, as well as in space, still faces complex and varied challenges.


Here are some of the major considerations and challenges involved in growing plants in space:

  1. Microgravity and environmental stress: Microgravity presents a major challenge to plant growth, as it affects the way water, nutrients and air are distributed to roots and stems. Plants may also find it difficult to anchor themselves in a low-gravity environment.

  2. Lighting: In space, plants do not receive constant sunlight, which is essential for photosynthesis. Artificial lighting systems must therefore be set up to provide plants with the right amount and type of light.

  3. Environmental control: Temperature, humidity and carbon dioxide concentration must be carefully controlled to create a favorable environment for plant growth.

  4. Resource recycling: Resources are limited in space, so it's essential to develop efficient recycling systems for water and nutrients to minimize the need for external supplies.

  5. Pollination: In the absence of insect pollinators, plants may require alternative pollination methods, such as hand pollination or the use of mechanical devices.

  6. Crop selection: Some plants are better adapted to growing in spatial environments than others. Researchers need to identify plant species that are more resistant and productive under these particular conditions.


Variations can influence plant growth. NASA's PESTO experiment in 2019 demonstrated that microgravity had an impact on the development of leaves, cells and chloroplasts in wheat plants. However, hypogravity was not unfavorable to the plants, which actually grew 10% faster than those grown on Earth.


Another major challenge is the poverty of extraterrestrial soils, particularly on Mars and the Moon. These soils are low in nitrogen and lack the organic matter essential for plant growth, such as carbon compounds. These conditions make it difficult to grow plants in these hostile environments. What's more, the absence of a magnetic shield on Mars and the Moon exposes plants to solar winds and cosmic radiation, potentially damaging their DNA. This radiation exposure is a potential risk to plant health and growth.


Finally, growing plants in microgravity requires a substantial amount of water, a resource that is extremely limited on Mars and totally absent on the Moon. Access to water is therefore crucial to the viability of any extraterrestrial gardening initiative.



Conclusion








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