Some ‘visionaries’ foresee the human race living on other planets. Sure, in principle nothing wrong with it.
However to really have any chance of survival in the long term that planet has to conform to very restricted parameters, as conditions found on earth since after millions of years having evolved as a species on earth our bodies are designed to live within the boundaries as set by the earth’s conditions.
Even a small relatively deviation in temperature is enough to make human life very hard reason why so few people live on the poles and why the human race had it’s origins nearer the equator.
We need a temperature within a narrow band to survive.
Now take for example the planet Mars.
It’s dead. It died long time ago, it’s atmosphere consists of for us unbreathable gases (mostly CO2) at about half earth’s pressure making surface life impossible.
It doesn’t have a revolving iron core so no magnetic field to deflect hard radiation making surface life impossible
The water content of the planet consists mostly of permafrost at <250 kelvin making the availability of liquid water near enough impossible.
The surface consists of oxidized rock and a good layer of micro particle dust making articulated earth like machines of any usable size a nearly impossible task to keep operational.
The same dust will enter into any construction made by us and in the long term cause any machine or living entity being perfused by that dust.
This dust is mostly iron oxide. Surface of Mars As an abrasive compound it really does the trick. It is toxic in the amounts found in Mars surface and atmosphere.
It is certainly a compound which will destroy any larger machine due to it destroying bearings and being and electric conductor short circuiting any electronic device, which cannot with our present or to be foreseen technology be totally sealed off.
Than the daily dose of radiation. Already the even the shortest Earth-Mars round trip would be about 0.66 sievert. This amount is like receiving a whole-body CT scan every five or six days. Conditions on Mars aren’t any better due to lack of dense atmosphere and magnetic field. Radiation on Mars
So only subsoil habitation is possible and than at great depth. In order to construct a habitat suitable to sustain multiple generations we need to excavate about the size of the current habited surface of earth which including the surface needed for agriculture (based on 2018 population) Earth has a land surface of 149 million km².
Which needs to be heated since the planet is at <250 kelvin. It also needs to have daylight lighting, earth like atmosphere and pressure. The energy needed to just begin to excavate a small colony, heat it, pressurize it and give it earth like atmosphere is beyond calculation. And how does one obtain this energy? Solar panels won’t work since the sun is to distant, windmills won’t work due to the low density of the atmosphere.
Only one energy source would be direct matter to energy conversion as in nuclear fission and/or fusion. But it would have to be a really huge reactor, or field of reactors to generate this energy. But how do you build that on Mars? How do you build the infrastructure? For that you need energy you don’t have yet.
In other words, to have a real self sustaining colony on Mars which won’t cause inbreeding within one generation you need to deplete all resources on Earth, send them to Mars, invent robots that will reliably prefabricate the living quarters and other infrastructure. After the decennia it takes to do that send at least 100.000 of humans of diverse populations to Mars and hope they won’t kill each other on the trip and the cosmic radiation doesn’t cause a significant mutation.
In conclusion the ‘visionary’ which proposes making Mars an alternative for Earth suffers from an overly active imagination and sincere lack of factual knowledge/comprehension thereof