[acdha]

Right, which is both well known and not the question at hand. The point remains that a closed loop hasn’t been demonstrated under much easier conditions on earth and therefore it’s clearly not the easy task the person I replied to described it as.

[somenameforme]

All travel in and out of Antarctica is cancelled during the ~7 months of winter. So all of that is being done without external inputs during that time frame. A permanent (or at least practically permanent) closed loop is probably not possible because of the countless treaties. It severely limits what can be built, which local resources can be utilized, and even what you can do with your own waste.

[gamblor956]

The Antarctic treaties allow for the development of greenhouses, etc., for scientific research purposes (in areas that have already been developed).

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.

[somenameforme]

You're going to need to cite that because to my knowledge there's been 0 efforts towards any sort of long term self sustainability on Antarctica. The most I know of are the efforts to reduce diesel consumption, but that's probably more gesturing towards this 'green' political stuff than any effort at self sustainability.

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.

[gamblor956]

Sample on long-term sustainability efforts in Antarctica: https://en.mercopress.com/2009/02/18/zero-emission-energy-se...

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.

[somenameforme]

That's not about long-term sustainability. It's just the doing away with diesel stuff, which is largely irrelevant.

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.

[1] - https://en.wikipedia.org/wiki/Sabatier_reaction

[gamblor956]

I think your vision of Mars is based on Hollywood.

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.

[acdha]

It’s done with at least two external inputs (air, water) and far more resource availability than a Mars mission would have. A long-term closed loop isn’t banned by treaties - McMurdo alone is like 50 acres and a hundred buildings, something the size of a plausible interplanetary mission at our current technology level is not going to dramatically exceed that footprint.

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.

[somenameforme]

Mars has more than sufficient resources to provide practically endless air and water as well.

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.