As long as you have a dozen potatoes, some human poop, a sample of earth soil for necessary nutrients and bacteria, and rocket fuel to burn to make water, it should be pretty easy.
https://www.nature.com/articles/d41586-024-01158-6
Another way of looking at: have humans over-wintered in Antarctica without relying on outside inputs? That’s a much easier problem on multiple scales (oxygen, soil, temperature, water, etc.) so I wouldn’t take any mars proposal seriously before they’ve sent the same equipment to Antarctica and survived longer than the proposed mission.
Taking a piss outside is illegal, even peoples crap has to be collected and shipped back home. Any sort of development is essentially impossible.
And that article is an interview with the hipster cartoonist who wrote a largely junk science book on Mars..
And, yes, I linked to a best-selling popular science book at the level of the conversation here. I should note that the book has two authors, and the first one isn’t the illustrator but the professional biologist. You’re welcome to provide dissenting views if you want, I’m sure they wouldn’t claim to be the last word on the topic.
So for instance, their very first effort is to try to 'debunk' the idea of having Mars as a sort of 'backup' to Earth by claiming that even in the case of a doomsday event Earth would still be far more hospitable than Mars. That statement is completely true but also completely irrelevant.
Take a typical doomsday event, an asteroid impact or a supervolcano. Both kill you the same way which isn't the initial event, but rather the sun ending up getting blotted out for years by mass debris/ash not only causing an extreme freeze across the planet, but also ending photosynthesis rapidly killing all plant life which starts a mass extinction on up the food chain to animals that ate those plants then animals that ate those animals and so on.
This is the sort of event that could easily completely kill off humanity, but it's not because it'd make Earth a worse place than Mars. Even at the climax of mass extinction, Earth would still be dramatically more hospitable than Mars. The reason it will be so deadly is because it's so different than the conditions to which we prepare for -- more people die in the desert of drowning than of thirst. An offworld colony in this case would help ensure humanity is perpetuated, Earth is recolonized, rescue survivors, ensure global order, and so on. In fact this is the case for most of all conceivable disasters.
I wanted to dig into more of their arguments but this is already fairly lengthy. If you mention what you found most compelling, I can offer the data (or, as in this case, logic) to the contrary.
[1] - https://www.polartrec.com/expeditions/antarctic-weather-stat...
And scientists residing there have tried to make a closed-loop system for decades now. They haven't succeeded yet. It's a lot harder to do than fiction and Hollywood would have you believe. Importantly from the Martian colonization perspective: it's irrelevant that the scientists in Antarctic can't use local resources to build their closed loop, because that's part of proving the Martian concept, where there aren't any usable local resources.
And saying there are no usable local resources on Mars is ignorant of basic plans - sunlight, regolith which can be processed, hydrated minerals, CO2, water, and more. In the longer term the other various minerals and metals will also be highly useful, but those I listed are valuable right off the bat and easily accessible.
Mars has lots of resources. They're simply not usable with current technology without extreme amounts of energy.
Mars also gets significantly less sunlight than Earth (43%), so solar isn't going to solve the problem.
And you're spewing nonsense on Mars - all of the resources I mentioned are obviously directly accessible with minimal energy requirements. The one thing you're right on is that solar will never be a primary source (at least not without extensive and heavily redundant battery backups) because of intermittency and unreliability.
Fortunately we have the Sabatier reaction. [1] CO2 + H2 => methane + water. Given the atmosphere on Mars is about 96% CO2 and H2 is readily extractable from the vast water ice resources (or even the dirt if necessary), we've got access to basically endless methane on Mars. And on Mars we'd love to dump as much as we possibly can into the atmosphere. Early expeditions will also probably bring along some largish radioisotope generators again for the sake of emergency power generation. In a domain where one failure means everybody dies, redundancy is nice.
The Sabatier reaction is inefficient; as Wikipedia notes, it requires 17 MWh to produce a single ton of methane, not including the energy costs associated with electrolysis of local water sources for the H2. Hydrogen represents about 1/4 of the weight of methane, and so you'd need another roughly 0.4 MWH for the electrolysis, for a total of 17.4 MHh to produce 1 ton of methane.
Each MWh is roughly the energy needed to power 1000 homes. That's not some "largish radioisotopes." That's a full-scale power plant. We don't have many power plants that can produce that sort of output but which are light enough to launch into space or simple enough to be assembled on-site. Solar (the easy option) would require a minimum of 15-20 acres on Mars, and approximately 120 tons of solar panels, not including wiring and other supporting infrastructure. We don't have any spacecraft capable of taking that much weight, so that's multiple orbital launches and multiple spacecraft just to get the solar panels to Mars, and we haven't even started discussing the weight or other equipment needed to get the solar panels down to the surface, let alone transport the habitat modules or other equipment, or the astronauts and colonists making the journey.
TLDR: Mars is a pipe dream with current technology.
Hollywood, so far as Mars is concerned, is mostly based on the Martian which is a hard sci-fi and phenomenally well researched book. The mistakes it made, inadvertently and intentionally, only make Mars colonization even easier than demonstrated. For instance the raging dust storm of the movie (and book) does not exist (and was an intentional fib). Low atmospheric pressure means the most fierce dust storm would have all the force of a very light breeze. And similarly his adventures to extract water from the rocket fuel were completely unnecessary as it turns out the seemingly barren regolith is surprisingly moist at 2-11% water by mass, an unintentional mistake as this was only discovered after the book was published.
Again, I’m not saying it’s inconceivable that it could be done, only that it’s harder than the sales guy would have you believe.
Beyond that I think you're also on a red herring here. There's no plan for a long-term closed loop on Mars to begin with. In the distant future most likely, but complete self sustainability is not practical in short to mid term timeframes. That would require essentially duplicating absolutely all forms of industry on Mars which probably will happen but only in the very distant future. In the interim a Mars colony would be receiving regularly shipments from Earth, and those return trips would also enable colonists, who decide it's not for them, to also return to Earth.
So all you really need is hydrogen. And conveniently part of the water you produce or harvest can be split into H2 and O2.
The absurd convenience of such things realllly makes one think more deeply about the simulation hypothesis.