My recent article on settling Mars has generated a lot of discussion, some of it around the basic concept of how difficult it is for humans to live anywhere but a thin envelope of air hugging the surface of the Earth. This is undoubtedly true, as I have discussed before – we evolved to be finely adapted to Earth. We are only comfortable in a fairly narrow range of temperature. We need a fairly high percentage of oxygen (Earth’s is 21%) at sufficient pressure, and our atmosphere can’t have too much of other gases that might cause us problems. We are protected from most radiation that bathes the universe. Our skin and eyes have adapted to the light of our sun, both in frequency and intensity. And we are adapted to Earth’s surface gravity, with any significantly more or less causing problems for our biology.

Space itself is an extremely unforgiving environment requiring a total human habitat, with the main current technological challenges being artificial gravity and radiation protection. But even on other worlds it is extremely unlikely that all of the variables will be within the range of human survival, let alone comfort and thriving. Mars, for example, has too thin an atmosphere with no oxygen, no magnetic field to protect from radiation, it’s too cold and its surface gravity is too little. It’s better than the cold vacuum of space, but not by much. You still need essentially a total habitat, and we will probably have to go underground for radiation protection. Gravity is 38% that of Earths, which is probably not ideal for human biology. In space, with microgravity, at least you can theoretically use rotation to simulate gravity.

In addition to adapting off-Earth environments to humans, is it feasible to adapt humans to other environments? Let me start with some far-future options then finish with what is likely to be the nearest-future options.

Perhaps the optimal way to most fully adapt humans to alien environments is to completely replace the human body with one that is adapted. This could be a robot body, a genetically engineered biological one, or a cyborg combination. How does one replace their body? One option might be taking virtual control of the “brain” of the avatar (yes, like in the movie, Avatar). This could be through a neural link, or even just through virtual reality. This way you can remain safely ensconced in a protective environment, while your Avatar runs around a world that would instantly kill you. We are closer to having robotic avatars than biological ones, and to a limited degree we are already doing this through virtual presence technology.

But this approach has a severe limitation – you have to be relatively close to your Avatar. If, for example, you wanted to explore the Martian surface with an avatar, you would need to be in Mars orbit or on the surface of Mars. You could not be on Earth, because the delay in communication would be too great. So essentially this approach is limited by the speed of light.

You could also “upload” your mind into the Avatar, so that real time communication is not required. I put “upload” in quotes, because in reality you would be copying the structure and function of your brain. The avatar would not be you, it would be a mental copy of you operating the avatar (again, whether machine or biological). That copy would feel like it is you, and so that would be a way for “you” to explore a hostile environment, but it would not be the original you. However, it may also be possible, once the exploration has concluded, to copy the acquired memories back to you. It may also be possible to do this as a streaming function. In this case the distance does not matter as much, because you have a local copy with real time interaction, while you are receiving the feed in a constant stream, just delayed by the communication time. Because the avatar is a copy of you, the original you would not need to send instructions, only receive the feed. So you could be safely on Earth while your mental twin avatar is running around on Mars.

A more advanced version of this is similar to the series Altered Carbon. In this hypothetical future people can have their minds transferred (again, copied) to a “stack” which is essentially a computer. The stack, which is now you, operates your body, which is called your “sleeve”. This means, however, that you can change sleeves by pulling our your stack and plugging it into a different sleeve. Such a sleeve could be genetically engineered for a specific environment, or again it could be a robot. This envisions a future in which humans are really digital information that can inhabit biological, robotic, or virtual entities.

So far these options are pretty far in the future. The closest would be using virtual reality to control a robot, which is currently very limited but I can this being fairly robust by the time we could, for example, get to Mars. Another approach which is also fairly near term (at least more than the other options) is to use genetic engineering, medical interventions, and cyborg implants to enhance our existing bodies. This does not involve any avatars or neural transfer, just making our existing bodies better able to handle harsh environments.

For existing adults, genetic engineering options are likely limited, but could still be helpful. For example, inserting a gene that produces a protein derived from tardigrades could protect our DNA from radiation damage. We could also adapt our skin to block out more radiation, and be resistant to UV damage. We could adapt our bones and muscles to different surface gravities. We may even find ways to adapt to microgravity, allowing our bodies to better handle fluids with gravity.

For adults, using medical interventions, such as drugs, is another option. Drugs could theoretically compensate for lower oxygen tension, radiation damage, altered cardiac function, neutralizing toxins, and other physiological responses to alien environments.  Cyborg implants are yet another option, reinforcing our bones, enhancing cardiac function, shielding light or radiation, or adapting to low pressure.

But we could more profoundly adapt humans to alien environments with germ line genetic engineering – altering the genes that control development from an embryo. We could then make profound alterations to the anatomy and physiology of humans. This would create, in essence, a subspecies of humans, adapted to a specific environment – Homo martianus or Homo lunus. Then we could theoretically include extreme adaptations, to temperature, air pressure, oxygen tension, radiation exposure, and surface gravity. These subspecies would not be adapted to Earth, and may find Earth as hostile and we find Mars. They would be an offshoot of humanity.

Even the nearest of these technologies will take a long time to develop. For now we need to carry our Earth environment with us, even if it is within the confines of a spacesuit. But it seems likely we will find ways to adapt ourselves to space to some degree.