The problem with both the “Colonize Mars!” and the Bio-Dome/Dr. Strangelove-esque underground bunker approaches to surviving catastrophe is that they ignore how the underlying prerequisites of human civilization—even post-industrial societies—are fundamentally tied to the global biosphere of the surface and oceans Earth and how difficult it is to recreate Earth-like habitable conditions on Mars or elsewhere, even in deep mine shafts, and notwithstanding how separation from the environment which we have evolved in would impact human beings on both an individual and societal level. We are so accustomed to virtually free access to all nature of environmental resources, from air and water to the just-so filtered radiation and plant nutrients, that we don’t think about just how many layers of systems are needed for efficient availability and recycling would be necessary to sustain even a modest population of human beings necessary to maintain even a minimum level of social interaction, basic skill base, and genetic diversity.
A truly self-sustaining “colonization” on Mars is very likely a nonstarter; even though there is water (in sparse amounts, largely in extremely briny recurring slope lineae or in an underground polar lake) it is not distributed enough to support diverse colonization nor is there any kind of hydrological cycle. The surface of Mars lacks much in the way of the nitrates necessary for agricultural cultivation (though there are signs that at least trace amounts may be found deeper in the regolith); but worse, the soil is contaminated with large amounts of toxic perchlorates which would have to be laboriously and intensively washed out with that precious water to be useful as a substrate for plants; the alternative is hydroponics, which works great for marijuana or hothouse tomatoes but is no basis for intensive grain agriculture. The real kicker, though, is the Martian gravity; at 38% of Earth normal, it is likely to have some long term physiological effects, and would likely cause difficulties in natal and childhood development beyond the common trope of musculoskeletal weakness. The costs of transporting all of the necessary infrastructure to extract resources is unimaginable, even assuming several orders of magnitude reduction in space launch costs.
Underground cities suffer from the opposite problem; all of the conditions and resources (air, water, soil) to reproduce terrestrial surface-like conditions exist, but expanding and accessing resources will be challenging, especally if the surface is rendered completely uninhabitable by some hypothetical disaster. Talk to a submariner who has spent a few deterrence tours in a boomer and he’ll tell you how claustrophobic life is, not just because of the small compartments and cramped conditions but because there is no sky for months, which is why the greatest treat is to be able to take a rare few second peak through a periscope just to have a glimpse of the horizon.
Off-planet colonization will almost certainly require one of two developments; either solar-orbiting large diameter rotating space habitats made with space-based materials, to economically produce sufficiently Earth-like conditions and support the necessary hydrodynamic and thermodynamic cycles necessary for a comprehensive, self-contained ecosystem. Even that would require the development of a space resource extraction and delivery infrastructure that is well beyond what can currently be done even with a focused effort, and will require significant bootstrapping and automation to become viable.
We are far better off—for the time being, certainly, and likely for the foreseeable future—to take all necessary steps to preserve and protect our own planet, which we have specifically evolved to inhabit to the extent that we do not generally realize just how much it provides for us. I don’t mean this in a mystical “Gaia”-like spiritually sense, but in the very grounded sense of systems ecology as outlined by researchers like Vaclav Smil (see The Earth’s Biosphere: Evolution, Dynamics, and Change, Harvesting the Biosphere: What We Have Taken from Nature). And protecting our planet—both from our own excessive desires and from external threats—is vastly cheaper than any interplanetary colonization or mass underground civilization plans which has the benefit of also developing the kinds of technologies needed for eventual extraterrestrial habitation.
Stranger