On January 3, 2019, China's Chang'e-4 lander touched down on the far side of the moon and deployed the Yutu rover. In addition to its many instruments, the rover carried an important science experiment known as the Biological Experiment Payload (BEP). Over the next eight days, this payload conducted a vital experiment where it attempted to grow the first plants on the moon. Included in the payload were cotton, potato, arabidopsis, and rape seeds, along with fly eggs, yeast, and 18 ml (0.6 fluid oz) of water, which was kept at a constant atmospheric pressure.
An important addition to that may explain why: The lunar night approached -150° C and the experiment failed to keep the steady 24° C that it was supposed to maintain, so the plants died. I don’t think it was because growing plants on the moon is intrinsically impossible.
I also wonder how they expected 18 mL of water to last more than a few days anyway. Perhaps someone smarter than me can answer that.
In a closed system the water isn’t going anywhere, so it’s possible that a very small amount of enough for 100 days.
I’m not a space gardener, though.
In any enclosed system the water circulates through the plant, evaporates into the air, possibly condenses on surfaces, then is drawn back into the plants again. There is no need to add water as long as there is enough tongo through the cycle.
This was basically a heated terrarium that did not stay warm enough.
The entire farm was about the size of an ice cube tray, and had a growing volume of about 2 cups. Terrariums in general would use about 6 tsps for a 2-cup terrarium; the Chinese experiment used about 3.5 tsps. I’m not sure why they used that amount of water; I would speculate (and it’s only speculation) that the plants they choose didn’t need more, or possibly the lower gravity on the moon meant that the water was generally more accessible to the plants.
2 week long nights will kill any plant, at least down to the roots. 2 week long days will kill most. Can’t garden on moon. Not without grow lights. Maintaining temperature isn’t enough.
Plants grow mostly by sucking water into their cells, so the water should soon end up stuck in the plants if everything else went right. I suppose they did count with it, but 18 ml of water is still suprizingly little.