On January 3, 2019, a pivotal moment in space exploration occurred when China’s Chang’e-4 lander made a historic touchdown on the far side of the moon. As part of this mission, the lander deployed the Yutu rover, which carried a groundbreaking science experiment known as the Biological Experiment Payload (BEP). Over the following eight days, the BEP embarked on a groundbreaking endeavor – the first attempt to grow plants on the moon. Within this payload were seeds of cotton, potato, arabidopsis, and rape plants, along with fly eggs, yeast, and a small quantity of water, all maintained at a constant atmospheric pressure.
The outcomes of this experiment hold immense significance for the future of space exploration, particularly in the context of Bioregenerative Life Support Systems (BLSS), critical for habitats and missions beyond Low Earth Orbit (LEO). Recently, a team of Chinese scientists released a study reviewing the experiment, its findings, and the potential implications for lunar, Martian, and deep-space missions. Their conclusion, somewhat revolutionary, asserts that plants can indeed thrive on the moon, despite the intense radiation, low gravity, and prolonged exposure to intense light.
This accomplished team of researchers hails from prestigious institutions such as the Center of Space Exploration, the College of Aerospace Engineering, the Key Laboratory of Biology and Genetic Breeding for Tuber and Root Crops at Chongqing University, the University of Electronic Science and Technology of China, and the Laboratory of Space Biology at the Chinese Academy of Agricultural Sciences in Chengdu. Their comprehensive analysis and findings were published in two separate papers, featured in Microgravity Science and Technology on June 20, and Acta Astronautica on October 17, 2019.
The significance of cultivating plants in lunar, Martian, and space habitats cannot be overstated. Beyond providing a sustainable source of nutrition and reducing dependence on resupply missions, these crops play a pivotal role in recycling carbon dioxide, generating fresh oxygen, and boosting the overall well-being of astronauts. Unlike conventional Environmental Control and Life-Support Systems (ECLSS), which rely on mechanical components that deteriorate and require replacement, bioregenerative systems possess the remarkable capacity to self-sustain over time. This inherent quality positions BLSS technology as an ideal choice for deep-space missions where resupply opportunities will be infrequent.
For years, astronauts aboard the International Space Station (ISS) have conducted experiments on plant growth and algae, including projects like the Vegetable Production System (Veggie), the Passive Orbital Nutrient Delivery System (PONDS), the Advanced Plant Habitat (APH), and the Plant Habitat Avionics Real-time Manager (PHARM). However, uncertainties persist about how the natural environment of extraterrestrial bodies may impact BLSS functionality.
Xie Gengxin, a Professor of environmental engineering at the Center of Space Exploration, Chongqing University, and the chief designer of the BEP, highlighted the necessity of plant cultivation in space for the establishment of bases beyond Earth: “When establishing a survival base on the moon, Mars, and other extraterrestrial planets, it is impossible to transport more things from the Earth. The need for in-situ use of resources for the production of oxygen and food is particularly important and is the first step to establishing a survival base, so plant planting experiments are very important.”
The Biological Experiment Payload (BEP), developed at Chongqing University, marked the first-ever biological experiment carried out by humans on the far side of the moon. The primary objective was to evaluate the impact of lunar surface conditions – characterized by low gravity, intense radiation, and prolonged exposure to intense light – on the growth and well-being of terrestrial organisms. The BEP payload encompassed a diverse ecosystem, with cotton, rapeseed, and potato seeds serving as producers of oxygen and nutrients through photosynthesis. Fruit flies played the role of consumers, while yeast acted as decomposers, breaking down waste from the flies and expired plants to generate additional nutrients. The experiment was unique, as it utilized natural sunlight on the moon for photosynthesis, rather than relying on artificial lighting. Additionally, the biological payloads were not equipped to shield against radiation, further confirming that plants could flourish under the moon’s challenging radiation conditions.
Shortly after the lander reached the lunar surface, adjustments were made to maintain a temperature of 24°C (75.2°F) within the biosphere, and the seeds were watered. By January 15, it was reported that cottonseed, rapeseed, and potato seeds had sprouted, accompanied by images from inside the BEP. However, the experiment faced challenges as the lunar night descended, causing external temperatures to plummet to -52°C (-62°F) and making it increasingly difficult to maintain a suitable temperature. Eventually, temperatures reached a frigid -190°C (-310°F), and the experiment’s duration was cut short at nine days, rather than the initially planned 100 days. Despite the difficulties, valuable insights were gained.
Xie Gengxin emphasized the significance of the findings: “Although our plants can grow in the natural sunlight and radiation conditions of the moon, the safety of these plants has not been evaluated. Whether it is healthy or not needs further research. Our experiments also show how difficult it is to survive on the moon and how to survive the lunar night. Our first biological experiments on the moon for humankind fully demonstrate that a regenerative ecosystem can be built on the moon to establish a human base.”
Looking ahead, Xie and his colleagues are planning to conduct further experiments in stable lunar lava tubes, which are being considered as potential base locations. “For the first time, we have sent six species from the Earth to the moon to conduct biological experiments, which has made an important milestone in establishing a base for human survival on the moon,” Xie noted. “Our team is now conducting research on how to establish a human base and space farm experiments by using lunar lava tube caves.”
As NASA and China plan to return astronauts to the moon in the coming years, with the goal of establishing a permanent human presence, the lessons from this lunar plant experiment hold paramount importance. A sustained supply of food, breathable air, and overall crew health, both physical and psychological, will be integral to the success of these missions. The research findings pave the way for a future where astronauts carry essential elements of Earth’s biosphere with them, ensuring their ability to live, work, and thrive in the demanding environments of extraterrestrial worlds. These endeavors represent a significant step toward the ultimate goal of a permanent human presence on the moon and further-reaching deep-space exploration.