Every aspect of human physiology is highly dependent upon the very specific (and, as far as we currently know, unique) conditions found on Earth. Everything from the salinity of our bodily fluids to the atmospheric pressure and composition we need to breathe, the minerals we require in our diet, even exposure to sunlight and the diurnal day&#x2F;night cycle.<p>At the risk of sounding metaphysical, we are as much a part of the Earth as your kidney is a part of your body. Yes, we probably can take your kidney out and keep it alive via artificial means for a certain period of time (it&#x27;s just an engineering problem) but it is a rather large leap to do so permanently. It&#x27;s worth asking whether the effort even makes sense.