快猫短视频

China鈥檚 Chang鈥檈 4 lunar lander captivated global attention when a cotton seed on board became the first plant ever to germinate on another world 鈥� and now the engineer behind this moon garden has revealed just how it was done.

Cotton, Arabidopsis, potato and rape seeds, as well as yeast and fruit fly eggs, were all inside a 2.6-kilogram mini biosphere when Chang鈥檈 4 landed on the far side of the moon in January 2019.

Months of uncertainty and planning led to the successful mission, says Xie Gengxin at Chongqing University, the experiment鈥檚 chief designer.

The idea to send a biosphere to the moon was selected from 257 suggestions submitted by Chinese students in 2016.

Rice and Arabidopsis have been grown on China鈥檚 Tiangong-2 space lab and plants have been cultivated on the International Space Station, but those experiments were conducted in low Earth orbit, at an altitude of about 400 kilometres. The cosmic radiation on the moon 鈥� 380,000 kilometres from Earth 鈥� makes it a more challenging environment.

Given limited space on the lander, the experiment had to be small and light, says Xie. The cylindrical capsule his team designed was 19.8 centimetres high with a diameter of 17.3 cm. It had a rectangular seedbed inside, measuring 800 cubic centimetres. A pipe built into the top allowed sunlight to reach the plants, and the whole chamber was kept at Earth atmospheric pressure.A replica is currently on display in the Design Museum鈥檚 Moving to Mars exhibition in London.

The real chamber was powered on just under 13 hours after Chang鈥檈 4 landed, at 11.19 pm on 3 January. The first order of business was remotely watering the seeds with a measured spritz of 18 millilitres of water.

The team had to consider in advance a number of things that could go wrong during the mission, such as the possibility the water might not be released or be released too early, or the pipe that let in sunlight got blocked by moon dust, in addition to camera or data transmission failures.

The capsule had two built-in cameras that photographed the seedbed every 10 hours. Images confirmed that the seeds weren鈥檛 watered before Chang鈥檈 4 launched from Earth and that none of the seeds had sprouted prematurely.

Once on the moon, the cotton plant sprouted two leaves and its root system grew horizontally rather than down into the soil, probably as a result of the weak lunar gravity.

The team is uncertain whether the fruit fly eggs hatched, says Xie 鈥� if they did, they weren鈥檛 caught on camera.

The temperature on the surface of the moon reaches highs of 127掳C in daytime. But using two cooling plates, the team was able to limit the daytime temperature inside the biosphere to under 36.5掳C.

The plant lived for the equivalent of nine Earth days, until the moon鈥檚 far side turned away from the sun. Temperatures on the moon drop to -173掳C during lunar night, which lasts for a fortnight.

Though the team knew the plant wouldn鈥檛 survive the cold, the capsule wasn鈥檛 powered off until 9 May. After months of experimentation, the capsule had lost some air, with a pressure reading of 0.9 Earth atmospheres.

Future research will focus on how to improve and cultivate more ecosystems in space, says Xie.

鈥淚f astronauts or space tourists can breathe oxygen generated by plants and see living, green things in space, it鈥檚 sure to raise their spirits,鈥� he says.