My intuition suggests this is physically impossible. My assumption is that these habitable zones would be required to generate the necessities of life in an en

My intuition suggests this is physically impossible. My assumption is that these habitable zones would be required to generate the necessities of life in an environment devoid of any of them. Nutrients, oxygen, water... we could make recycling them very efficient, but there's always some loss. And even if you had zero loss, that's insufficient. If you're going to make a habitable zone that can support new population, you need to operate at a surplus. The other option if you can't manufacture these resources from nothing is to import them. But that's extremely expensive. That's not a problem if the recipient is generating something of roughly equivalent value, such as mining valuable resources that can be shipped back (classic colonialism), or conducting important research (as in the case of the ISS), but if the recipient isn't generating anything of value besides somewhere to run later, then it never really gets there because it relies entirely on receiving continued shipment from the motherland. I'm happy to be set straight on any of the above points, but these are the doubts that come to mind whenever someone argues the moon or Mars have potential as off-planet habitable zones.