Image: NASA

Tending crops may be important to any farmer, but in future space colonies, it could be a matter of life and death. So NASA scientists are already practicingand they are finding many obstacles to overcome.

On Earth, the process is quite simple: plants supply us with oxygen to breathe and food to eat; we supply them with carbon dioxide and fertilizer, which they convert back into oxygen and food. But in space, cultivating such self-sufficiency is a different story. Even the new International Space Station sports a strictly "mechanical" life-support systemmeaning that food and oxygen are brought up from Earth.

One problem with bioregenerative life-support systems in space is, well, space. There isn't much room on a spaceship or space station, so plants must have short stems and few inedible parts. They must also be able to grow well with little light, and the light source needs to be as efficient as possible to reduce energy demands. The wheat in the image shown here grows under light-emitting diodes (LEDs).

Another problem is weightlessness. Although plants can be kept from floating around, water and air tend to distribute evenly in the soil, which makes it more difficult for the plants to get them. Experiments have shown that very grainy soil lets air reach the roots but causes the water to scatter. In contrast, very fine soil passes water to the roots but clogs the airflow. Above the soil, poor air circulation can also suffocate plants, so fans of some kind are required. Microbes, too, are a must to break down biomass and provide nutrients and carbon dioxide.

A bioregenerative life support will probably never fully replace the mechanical one on the International Space Station, says Jay Garland, principal scientist for the Bioregenerative Life Support Project at Dynamac, Inc., at the Kennedy Space Center. At most, he adds, the astronauts might grow a small crop for fresh food. With the help of plants and microbes, however, future space stationsor outposts on the moon or Marsmay truly become worlds unto their own.