Plants just can’t survive in low-gravity conditions like on the Moon, two new papers suggest — they may choose to, at least based on which species will grow.
When Chang’e 4 arrived on the Moon in January 2019, it carried a cargo that could herald the future of space exploration: the seeds of four types of plants that wanted to grow on the lunar surface. The germination of a single cotton seed attracted much attention at the time, but there is more to germination than germination. If plants grown on the Moon are less productive or fragile than those on Earth, it will be a big problem.
It took more than four years, but important research results have now been released and suggest that of all the obstacles to establishing colonies on the Moon and Mars, growing food may not be the only one. Then again, it’s too early.
It is important to note that Chang’e 4 did not attempt to plant seeds on the lunar soil. Some experiments have shown that it is possible, although difficult. Instead, the test was whether the Moon’s gravity and high radiation would be a problem for plants. Gravity is the most important part of this question. After all, if the Sun’s rays, not filtered by the atmosphere, turn out to be harmful to plants, we can always find ways to soften the roof of the house in other countries. Replacing the low power that leaves and the knowledge of the degree can be a great challenge.
Chang’e 4 as seen by the Yutu-2 rover. Inside was a plant growing for the first time in another world.
Fortunately, however, it looks like that won’t be necessary. In fact, low gravity can help solve some of the difficulties that must be faced beyond the embrace of the Earth.
The first results comparing plants on the moon with those on Earth were released by a team from Chongqing University in June, and more information is now available. When Chang’e 4 did its thing on the Moon the authors placed the same seed in the same soil environment kept at the same temperature, humidity, and air pressure.
“We found that a gravity of 1/6 g accelerates seed germination,” the researchers announced in one of the papers.
Only one cotton seed, and none of the plants, grew on the Moon, contrary to contemporary reports. On Earth some canola plants sprouted, along with cotton seeds.
The biggest threat the moon plant faced was the long night, which began nine Earth days after landing. The temperature inside the lunar compartment dropped to 52°C (-61°F), so the ground control was cooled to match. Warmth did not return for about 18 Earth days.
Amazingly, the moonshine was still green and upright when the light returned. The measurements on Earth, were dead and dark-yellow in color. The plucky Moon-seedling survived the second day of the month although its growth stopped, which the researchers attributed to the lack of oxygen in the environment.
Researchers suspect that gravity has caused cold tolerance in some advanced polar crops, but it has long been out of control in warm-climate crops like cotton. Sadly, however, the cotton plant seems to die in the middle of the night of the second month, and during the five days of the month no other seed sprouts.
The authors attribute the failure of three other plant species to germinate due to temperatures exceeding their comfort zone in the first five days.
Despite the drawbacks, moon farming has potential benefits. Like the underwater agriculture described in this episode of our podcast Big Questionsit must be free of insects and weeds, so chemicals are used to control them.
Experiments on the International Space Station have shown that plants do not need gravity to grow and even bear fruit. However, these plants have often been combined with suitable conditions in all other ways. The fact that low-gravity cotton is able to overcome the cold is a revelation that can be seen as very important.
The ability to farm will be more important to Martian bases than their lunar counterparts. Getting food from Earth to the Moon will be expensive, but it won’t be nearly as prohibitive as Mars. With nearly twice the gravity of the moon, we hope that Mars will have a similar effect on plants.
The two studies were published in Microgravity Science and Technology and Acta Astronautica.
(H/T: Universe Today)