Biological life support systems, or biospheres, could now recycle enough oxygen, water and food to keep people alive for years. Two groups of four people lived in a sealed environment in China called Yuegong-1, or Lunar Palace 1, for a total of a year, with one group spending a record-setting 200 days in the facility without needing any outside materials, and they could have gone longer. The project aims to help China establish bases on the moon.

Details of the experiment, which ended in May 2018 …