After successfully landing on the far side of the Moon to deploy a rover, China’s Chang’E-4 has now taken up gardening. The craft brought seeds in a small container, and some of them have sprouted – despite the Moon’s low gravity. And while the Chinese news agency, Xinhua, reports reported that the experiment has now ended as the sprouts will not survive brutally low temperatures of the lunar night – which could be as low as minus 170 degrees Celsius – the seeds sprouting is still a major milestone towards future space exploration and possibly establishing a lunar base as a pit stop en route to other planets. “In this cold winter, the news of the spring on the Moon is warm,” as Zheng Yongchun, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences puts it, rather poetically.
But what can we actually learn from the deployment of a tiny, self-sustained, sealed garden?
The craft and its tiny garden touched down on the Moon on January 3. And just to be clear, Chang’E-4 won't be growing seeds on the lunar rocky surface itself – that is, in the regolith – in temperatures that veer between much colder and much hotter than what you’d find anywhere on Earth. Instead, the craft is tending to cotton seeds buried in earthly soil, brought along in the container. The jar also contains potato, Arabidopsis and rapeseed seeds, plus a few fruit fly eggs and yeast – all loaded by researchers from Chongqing University.
“The six organisms could make up a mini-ecosystem, with plants producing oxygen and food to sustain the fruit flies,” says Bernard Foing, the lead scientist of ESA’s SMART-1 lunar orbiter mission. “Yeast could process the flies’ waste and dead plants to provide another food source.”
While there have been several probes that have explored the Moon in the 1970s, including Soviet landers and Nasa’s manned Apollo missions, plus more recently the Chinese Chang’E-3 lander with its small Yutu (or Jade Rabbit) rover, none have ever grown plants there. When the Apollo missions brought back lunar rocks – the regolith – researchers sprinkled some of it on earthly top soil to check whether the regolith was toxic.
Researchers did perform many experiments on Earth though, growing seeds in a simulated lunar environment, as well as on the International Space Station – where algae and fungi survived about 500 days in space. The first seeds flowering in space were on a Soviet craft Salyut 7 in 1982.
But growing plants on the Moon, even in a sealed container, is very different. First, on the ISS there is essentially no gravity. “Not having gravity-driven convection makes it a real challenge to mix the air in a closed environment, and makes water delivery and management difficult as well,” says Anna-Lisa Paul, a space biologist at the University of Florida-Gainesville. On the Moon, there is some gravity – one sixth of Earth’s gravity – so this will be a lesser problem.
More worryingly, there is solar radiation. The Moon receives high particle radiation, much, much more than the ISS that is shielded by our planet’s magnetosphere. The sealed container tries to shield the plants inside, at least to a degree, but the conditions are much harsher.
The Moon also has extreme temperature swings - between day and night, and between areas that are exposed to the sun or covered by shade – with variations of 200-300 degrees Celsius in a single day. The container has a mechanism to transfer heat which should make it possible to maintain a temperature of about 20-30 degrees Celsius. According to Afshin Khan, an environmental scientist at the Blue Marble Space Institute of Science in Seattle, the heat control system is dependent on some kind of radioisotopic heat source, but the details are not clear. “What would be interesting though is if the heating system fails and the bioshpere chamber still remains active for a few days,” says Khan. That would give us very interesting answers. “That's science - even failure is good.”
Because of the very harsh environment of the Moon, the species selected in this experiment are both high and low temperature resistant, says Zheng. But they also need sunlight to survive. The sealed container is made of aluminium alloy, but light enters using a light pipe technology through an opening at the top of the jar, says Zheng. As for water, the lander carried 18 ml of it, and as it touched down, a pump poured the water onto the seeds. It's not exactly clear what the pump system is, but it is likely to be a syringe-based pump mechanism that will be releasing water in small amounts until it runs out, says Khan.
The aim is “to test photosynthesis and respiration,” says Clive Neal, a geologist at the University of Notre Dame. “Temperature control is critical given the extreme swings from lunar night to lunar day. No word on whether the fruit flies have hatched - they will need the oxygen from photosynthesis, but as the experiment is about to be placed in lunar night for a long while, photosynthesis won’t happen.”
Could this experiment lead to feeding a whole colony of future human space explorers on the Moon? Well, potatoes are widely regarded as an important food source – recall Matt Damon’s character in The Martian, who opted for potatoes to survive. Arabidopsis thaliana or Thale cress was a great candidate thanks to its simple structure and short growth cycle (researchers have grown it in the microgravity environment of the ISS in multiple spaceflight experiments). Cotton is one of the main agricultural crop varieties - it can be used for clothing and textile. And rapeseed is a common oil crop in southern China. “At the seedling stage, it can be eaten directly as a green leafy vegetable,” says Zheng.
But the crucial part of the experiment will be analysing the effects of the brutal solar radiation on biological systems - an important first step in understanding lunar astronaut’s physiology and health. The Moon spends about three weeks out of its four week-long orbit outside Earth’s magnetosphere and receives the full dose of solar energetic particles and galactic cosmic rays that include ions like iron that “act like bowling balls on pins to an organism’s DNA, causing mutations,” says Kirby Daniel Runyon, a postdoctoral planetary geologist at Johns Hopkins Applied Physics Laboratory. “We also don’t know how the human body reacts long-term to the Moon’s gravity, which is 17 per cent of Earth’s, but obviously much more than the near-zero gravity of the ISS.” So China’s biological experiments on the Moon are “an exciting and necessary early step” in keeping future astronauts healthy, he adds.
What's the next step? Growing seeds directly in the lunar regolith. It's unclear when it might happen on the Moon itself, but multiple experiments will continued to be carried out on Earth. One project is called Off Planet Research, and it aims to determine what mixture of lunar Highland and Mare regolith could be the best for growing crops. The lunar Highlands are the lighter coloured areas on the Moon where anorthosite makes up most of the regolith. Anorthosite loves to soak up and hold onto water and is commonly used as a soil amendment here on Earth.
“The issue is that the darker areas on the Moon, called Mare, have most of the mineral nutrient components that plants love because the regolith in those darker regions is made mostly of basalt,” says Vince Roux, lead researcher at Off Planet Research. Basalt soils, like those found near volcanoes on Earth, make up some of the best farmland - but basalt does not absorb and store water as well as anorthosite. So ideally, any future lunar farm should have a mixture of the two types of regoliths, he says, plus a few additives.
But here is the problem. While previous tests showed that regolith isn't toxic as such, it can be dangerous due to its high percentage of super-fine particles. So it'll have to be treated before using it to grow food. NASA and ESA have already done a lot of work on just that, and the idea is for the regolith to be sifted outside the base to remove as many of the dangerous tiny particles as possible, and then also treated with water and some additives to condition the material before any seeds are planted, says Roux.
Despite all these future challenges, one thing is clear: the Chinese have now proven without a doubt that growing plants on the Moon is doable. “The question we all need to ask now is how to do it best using lunar regolith and in a way that will reliably feed the future residents of the Moon,” says Roux.
This article was originally published by WIRED UK
