Many scientists feel that the only way a manned mission to Mars is going to be possible is if the ship that makes the trip can re-create a tiny version of the closed environmental system that exists on Earth. A closed environmental system means that every living thing inside a Mars-bound ship must absolutely depend on the other living things on board for survival. All waste must be completely recycled through the system. Scientists call the process "closing the loop." As one element of such a closed loop, for example, crops would provide food and clean oxygen while also helping to purify and recycle the ship's water supply.
But copying the Earth's closed ecological system is easier dreamed of than done. Soviet scientists have been working on one part of this problem longer than anyone. For years, they have been testing the possibility of growing crops in space. After many frustrating efforts in their Salyut space stations, they eventually succeeded in raising wheat, oats, peas, carrots, dill, and a few other crops using a machine they call Phyton.
Researchers at NASA are hoping to close the loop further with their Controlled Environmental Life Support System (CELSS). The purpose of CELSS -- a sealed cylinder twenty-three feet high and ten feet in diameter that uses artificial light and a mixture of water and nutrients to grow wheat--is to create a system that can regenerate itself.
The success of such work will go a long way towards determining whether or not long space voyages will be possible and affordable.
Without a regenerating system, completely provisioning eight crew members for even a short mission to Mars would require eleven tons of water, air, and food--a load that today would cost about $65 billion to launch.
