I don’t think anyone’s arguing current technology would allow self-sufficiency. But part of the case for offworld settlements is that they very strongly incentivise technolology that would.
In the medium term, an offworld colony doesn’t have to be fully independent to afford a decent amount of security. If it can a) outlast some globally local catastrophe (e.g. a nuclear winter or airborne pandemic) and b) get back to Earth once things are safer, it still makes your civilisation more robust.
I don’t think anyone’s arguing current technology would allow self-sufficiency. But part of the case for offworld settlements is that they very strongly incentivise technolology that would.
In the medium term, an offworld colony doesn’t have to be fully independent to afford a decent amount of security. If it can a) outlast some globally local catastrophe (e.g. a nuclear winter or airborne pandemic) and b) get back to Earth once things are safer, it still makes your civilisation more robust.