There's still more to prove. China has to show that the plants can continue to grow, and that's no mean feat between the widely varying temperatures and the lower gravity. The lander has to make dramatic changes to preserve the biosphere's conditions and keep its interior relatively consistent.

Even with those challenges, this represents a significant milestone: it suggests that astronauts will have a realistic chance of growing plants on missions to use for food, oil and other resources. That could lighten the cargo load for long-term missions to the Moon and Mars, and could make it possible to stay after some initial supplies run low. Extraterrestrial farms are a long way off, but they're at least sitting on the horizon after this achievement.