Travel to distant worlds will test the limits of human adaptability, but will it break them? Given enough time, and basic needs like oxygen, humans can acclimate to new climates in a matter of weeks, months or years. But how do you become accustomed to different gravity, different lengths of season and day, and sunlight that just looks "wrong?"
As anyone who's lived in the Great White North can tell you, the quality, color and quantity of ambient light exerts an enormous psychological impact on mood and productivity. We respond to these aspects of everyday life in our deepest lizard brains; they transcend the executive mind's control.
Some groups, such as the transhumanists, believe human beings will one day voluntarily transform themselves into something beyond human, whether through slow technological and biological adjustments or wholesale shifts, such as downloading our consciousnesses into machines.
In the U.S., the National Science Foundation, Department of Commerce and Department of Defense (DOD) are already looking into technologies such as nanotechnology, biotechnology, information technology and cognitive science, collectively known as NBIC, and how they might combat physical limitations and diseases [sources: Edwards; Roco and Bainbridge].
Take oxidative stress -- an overabundance of chemically reactive, oxygen-toting molecules (aka free radicals) -– which is linked to numerous disorders of the blood, brain, eyes, heart and muscles. In astronauts, radiation exposure causes most oxidative stress. NASA and the DOD have begun looking at targeted nanoparticles that could scavenge harmful free radicals, but are in the very early stages of research and nowhere near human trials [source: Goodwin].
The shelves of science fiction abound with examples of transhumanism and NBIC, and their effects on humans, society, ethics, culture and nature; these stories also contain warnings about what can happen when we tamper with these relationships.
Messing with our standard equipment might sound far-fetched, even repugnant, but history teems with ideas once thought objectionable. Would our ancestors have deemed it suitable to cut organs out of dead people and place them in living ones, or to fill our bodies with surgical steel and plastic tubes? Space might one day impel us to embrace far more radical solutions.
Imagine if engineers could design craft without food stores or life support because your mechanical body didn't require them. Visualize soaring through the upper atmosphere of Jupiter, or even a hard vacuum, in a body grown specifically for the purpose. Consider the possibility of a body that repairs itself far more quickly than yours can, or one that ages at a crawl; picture a brain with massively amped-up memory, or that can interface directly with machines.
Some of these ideas remain far in the future, but others might be closer then we think. Could nanotechnology and cutting-edge biotech hold the keys to terraforming Mars, or to altering our bodies to better withstand the rigors of space? Could cryonics efficiently preserve humans on long trips through space?
Until humans can protect themselves from the worst of space, robots could blaze a trail, building "stepping stones" -- such as fuel stations or bases -- in advance of us "meat bags." Back on Earth, telepresence might allow humans to participate through robonauts, like the one currently aboard the International Space Station (although, without further communications advances, the ever-increasing radio lag would make this increasingly impractical).
Of course, we could opt to stay behind as our robot minions scour the stars. But what fun is that?