Medical students remember this list as: “bones, stones, abdominal moans, and psychic moans.”
Biological adaptations to gravity don’t end there. When we stand, our heart, itself a muscular pump, has to work against gravity, pushing blood vertically in the carotid arteries that run from our heart to our brain. When deprived of the need to work against the force of gravity, the heart and its vascular system lose their physical condition, slowly taking athletes and turning them into couch potatoes.
The accelerometer system in our inner ear, otoliths and semicircular canals, are designed to provide the finest details about movement, sharing their inputs and outputs with the eyes, heart, joints and muscles. These organs are not considered “vital” in the sense that they are not necessary to keep the human body alive. As a result, the essential role they play in providing a finely calibrated sense of movement is often overlooked.
Like all the best things in life, you don’t really appreciate what you have until you lose it. Imagine a gently oscillating, nausea-inducing scene from which there is no escape. That’s what it feels like when the inner ear organs don’t function properly. And that can be caused by diseases, drugs, poisons and, as it turns out, the absence of gravity.
The impediments do not end there. There are other, less understood alterations. Red blood cell counts decrease, causing a type of spatial anemia. Immunity suffers, wound healing slows, and sleep becomes chronically disturbed.
> Deprived of the need to work against the force of gravity, the body loses physical condition, taking athletes and turning them into couch potatoes.
* * *
There are a number of formidable problems that accompany long-duration missions. The first is life support. How do we invent a system that can keep a crew of four alive for almost three years?
For space stations, breathable oxygen requires electrolyzing a constant supply of water. But there’s no easy way to resupply a team traveling to Mars, so several ingenious solutions to this problem have been proposed.
One involves a self-growth approach to life support and nutrition. It turns out that if you grow 10,000 wheat plants, you can generate more than enough oxygen to breathe and at the same time eliminate the human waste gas of carbon dioxide. Better yet, you have a partial source of nutrition. For a time, the Space Center had a team of four volunteers encased in a hermetically sealed tube, subsisting quite independently on this hydroponically grown, self-regenerating life support system.
And that’s all great, until you factor in the possibility of crop failure.
Another solution, discussed at a European Space Agency symposium on human space exploration, would be to grow vats of algae (which could be easier to maintain than wheat and would also provide a source of protein). Between that and wheat plants, you could get halfway to a diet of pizza-like foods (bread coated with flavored seaweed) and greatly reduce the weight and volume of food and life-support devices needed. for a mission to Mars. A Frenchman specializing in the field of regenerative life support explained to me how it could work, even going so far as to explain the recycling of urine and the use of feces as a source of fertilization.
