When it comes to space planting, you who care about space must remember the scene where Matt Damon planted potatoes on Mars in the movie "The Martian". If you like science fiction, you must also be deeply impressed by Yun Tianming's first video meeting with Cheng Xin after separating from Earth in a wheat field located in a three-body spaceship.
Martian potatoes from the movie The Martian
Although these are only science fiction, but in the 21st century, with the long-term scientific research station on the moon, Mars exploration mission and other manned deep space exploration missions, how to establish self-sufficiency in space has become an important research topic for major space countries, space planting is also one of the key breakthroughs.
At present, space planting is still in the stage of scientific research and experimentation, mainly carried out in the space station located in low Earth orbit, and the functional support provided by manned spaceflight itself is extremely limited.
The role of space planting in human space exploration
Space planting will be one of the key technical points for human beings to achieve space exploration in the future, and it is the ultimate goal of space planting to reduce or even eliminate the need for resupply from the earth by planting crops in space or alien planets.
Through space planting, it can provide astronauts with food and water filtration, and also help control cabin humidity; Metabolize carbon dioxide in the air and produce oxygen through photosynthesis to achieve gas circulation; By caring for and observing plants in space, it brings psychological benefits to human long-term space flight and improves their happiness in orbital life; In addition, the need for launch mass for long-term space missions can be reduced.
Challenges in space cultivation
Human-built space systems can provide an atmospheric environment for plants and protect them from solar radiation (space planting provides light through artificial light sources). However, the effects of microgravity, cosmic rays and strong oxidative stress on plants cannot be avoided, which is also a problem that needs to be studied and solved by key seedlings in space planting.
1 Microgravity
Many people think of space as a zero-gravity environment, which leads to weightlessness. This is a very common misconception. In fact, gravity is ubiquitous in space, and a more scientifically accurate term is microgravity. In microgravity, astronauts and objects in space appear weightless. Microgravity affects plants just as it does on any other creature in space.
Since plants are terrestrial creatures, it is important for humans to discover how changes in gravity affect plant biology. In particular, nutrient supply in roots, biogeochemical cycling of nutrients, and microbial interactions in soil substrates are particularly complex.
2 cosmic rays
Cosmic rays are a type of ionizing radiation that is difficult to defend against. Protons (or other heavier elements) are accelerated to the speed of light after being emitted from exploding stars. This strong radiation bombards the organism and destroys the molecular structure. Unlike solar radiation, cosmic rays are physically difficult to defend against.
The magnetic field generated by the Earth can deflect this radiation to keep the planet safe. But on space stations or planets without magnetic fields, this radiation is difficult to avoid, causing huge health problems for astronauts and plants.
3. Oxidative stress
In spacecraft systems, oxygen and carbon dioxide cycles can sustain human life and do the same for plants. The type of oxidative stress that plants experience in space is related to metabolism, which is an inevitable consequence of metabolism. Biochemical processes of molecular and energy conversion produce oxidative byproducts and reactive oxygen species that are harmful to cellular structures. In space, this oxidative stress is amplified in plants, and its causes are still being studied.
The origin of space cultivation
The earliest space planting experiments were mainly space breeding, which can be traced back to the 40s of the 20th century, led by Harvard University and the Naval Research Laboratory in the United States.
On July 9, 1946, a U.S. V-2 rocket launched a "specially developed seed strain" into space 134 kilometers, but the seeds were not recovered in the first test. This was followed by the launch and recovery of corn seeds on July 30 of that year, after which rye and cotton were tested accordingly.
On February 22, 1966, the Soviet Union conducted the "Kosmos 110" biological space test. The mission, which carried wet seeds and two dogs, returned to Earth after 22 days in orbit, some of which became the first seeds to germinate in space. Experiments have shown that the seeds of these space-traveled lettuce, cabbage and beans not only germinate in space, but also yield more when grown on Earth than controls on Earth.
Commemorative stamp issued by the USSR for the biological space test "Kosmos 110"
From January 31 to February 9, 1971, the seeds of 500 trees flew around the moon with the Apollo 14 spacecraft. These species, known in the United States as "moon trees," including torch pine, plane trees, maple trees, sequoia and Douglas fir, were planted and grown on Earth without detecting any changes.
Space cultivation during this period mainly stayed in the space breeding stage.
The development of space cultivation
Entering the era of the space station, space cultivation ushered in its real development. The hegemon at the beginning of this era was the Soviet Union, which was committed to space station technology, and the United States was tied up by the space shuttle.
In the historic Salyut 7 space station planting experiment in 1982, Arabidopsis thaliana was planted using the "Fiton-3 experimental microgreenhouse", which achieved seed-to-seed space cultivation for the first time. Plant growth eventually produces mature and bursting pods. Of the approximately 200 seeds, half are immature, and 42% germinate into normal plants. This is a landmark event in space botany.
Fiton-3 experimental miniature greenhouse
In 1997, the Soviet Union used the "Sevt" space greenhouse on the Mir space station to make "ultra-dwarf wheat" complete the first "seed-to-seed" plant growth experiment.
Of course, the United States did not stop at space cultivation, and in 1983 they conducted sunward tests on sunflower seedlings in microgravity on the space shuttle Columbia. Despite the absence of gravity, the seedlings still underwent rotational growth, suggesting that these behaviors were instinctive.
In 2008, ESA conducted plant growth experiments in microgravity using the European Modular Cultivation System on the Space Shuttle. Experiments have shown that plants can sense the direction of gravity even at very low levels of gravity. Since then, ESA has used the system to conduct ground-based experiments, placing 768 lentil seedlings in centrifuges to stimulate responses to various gravitational changes. Molecular biology studies have shown that plants change calcium signaling at extremely low gravity levels, which can affect root growth.
In 2014, data from BRIC19 aboard the International Space Station obtained the first complete RNA sequencing of Arabidopsis transcriptome, making it possible to monitor every gene in Arabidopsis.
In 2016, under the care of American astronaut Scott Kelly, zinnias bloomed on the International Space Station.
Zinnias cultivated in space
On January 3, 2019, the continental Chang'e-4 lunar lander landed at von Kármán Crater on the far side of the moon, including a 3-kilogram sealed "lunar microsphere" containing plant seeds and silkworm eggs to test whether plants and insects can hatch and grow together. Cotton germinated on the Chang'e lander and died quickly. Although the experiment did not produce the expected results, it was the first astrobotanical experiment conducted on the lunar surface.
In 2021, astronauts from the International Space Station conducted experiments on the cultivation of Chilean peppers, one of the longest and most challenging plant experiments conducted in an orbital laboratory. After the first pick in October, the astronauts sterilized the peppers and ate part of the harvested fruit, with the rest being brought back to Earth for analysis. The peppers are grown in the ISS Advanced Plant Habitat (APH) incubator.
Plants grown in space include: Arabidopsis, Chinese cabbage, tulips, caryophyllus, flax, onions, peas, radish, lettuce, wheat, garlic, cucumbers, parsley, potatoes, dill, cinnamon basil, cabbage, zinnia, red lettuce, sunflower, winged fern, hard oats and peppers.
Flowering and fruiting peppers on the International Space Station
The future of space planting
Since Mars is the most suitable planet for life in the solar system other than Earth, the application of space planting will mainly revolve around the self-sufficient space planting on Mars in the future.
Elon Musk, founder of Space Exploration Technology, is committed to making humans a multi-planet species by colonizing Mars. Musk has said that to achieve the sustainable development of human beings on Mars, it is necessary to build a city of 100,000 people on Mars, which requires 1,000 starships and 1 million tons of vitamin C, otherwise humans on Mars will slowly die in pain, just like the beginning of the great voyage of mankind.
Food on Mars will be grown in solar hydroponic farms underground or enclosed structures. Space planting still has a long way to go to achieve complete self-sufficiency for Martian colonies. But it is foreseeable that Matt Damon's scenario of growing potatoes on Mars will come to fruition in the near future.
Rendering of a hypothetical plant farm on the surface of Mars
Source: Space Exploration, Issue 2, 2022
Text/Wakasui
Editor/Yang Sishuang
Audit/Mu Tan
Executive Producer/Jiang Jun
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