NASA has announced plans to set up a greenhouse on the surface of Mars by the year 2021.
As humans start to colonize the moon and Mars, they will need plants and greenhouses. These will provide hood, help recycle the air, and will be an important link in recycling for space colonists. Plants evolved on Earth may find it difficult to live on other planets, even in greenhouses.
"When you get to the idea of growing plants on the moon or on Mars, then you have to consider the idea of growing plants in as reduced an atmospheric pressure as possible," Rob Ferl, molecular biologist at the University of Florida, said.
Advantages of growing plants in a low-pressure environment include reducing the weight of the air that will need to be carried to Mars. On Earth, we may not think of air as having significant mass, but carrying the gases will add significant weight - and cost to any future mission of colonization.
A second advantage to raising these varieties of plants concerns the structural strength of the interplanetary greenhouses. Mars an atmospheric pressure only one percent that on Earth, pressurizing such structures to Earth conditions could create undue stress on the walls. This would be greatly reduced if the greenhouses were able to operate around 1/16th of the air pressure on the surface of our home world.
When plants are subjected to these low pressures, they begin to behave as if they are experiencing a drought. As low pressures draw water out of the leaves, the plant struggles to replace moisture. Researchers raised humidity levels in the greenhouse to 100 percent, and gave the plants all the water they could use. Still, the defense mechanism continued.
Such actions on an alien world would expend energy in the plant, fighting a stress condition that does not exist. A colony would also need to expend its own precious energy pumping water and maintaining extremely humid conditions in the structures.
The same mechanism that forces water through pores in the leaf also has the same effect on hormones. It is possible that one day, low-pressure environments will be able to extract hormones from plants, like those that cause aging, before they can affect the organism.
"Astronauts aren't the only ones who will benefit from this research... For example, if you store fruit at low pressure, it lasts much longer. That's because of the swift elimination of the hormone ethylene, which causes fruit to ripen, and then rot. Farm produce trucked from one coast to the other in low pressure containers might arrive at supermarkets as fresh as if it had been picked that day," NASA wrote in a press release announcing the research.
