A material way to make Mars habitable
seas.harvard.edu
seas.harvard.edu
In the novel/TV series "The Expanse", Martians live underground in tunnels, because above ground it takes more material and energy to build air-tight buildings which also protect from radiation. And they still have adverse effects from the lower gravity.
One of the most fascinating aspects of that series is that there are three Human "subpopulations", two of which would have trouble to exist on Earth, physiologically.
Still, the thin atmosphere of mars would prevent any liquid water or plant life. So they must be talking about at least some more pressure.
The pressure needs to be high enough to prevent boiling and less dramatic effects on water or similar matter. There's a reason nothing grows above a certain altitude.
That's why I asked about a usable atmosphere...
And anyone living on Mars would probably have acclimated to a certain atmospheric pressure. Maybe it is beneficial for them to be "altitude adapted" or maybe it's not (oxygen capacity vs risk of embolisms).
That's of course assuming all the possible repercussions of being born and growing to adulthood in lower gravity that we don't yet currently know of have been accounted for and counteracted. I'm doubtful that training in higher gravity once an adult can negate the major negative effects of growing under lower gravity (which might include weaker bones), and so also doubt that a drug causing an even shorter term change can negate the negatives also.
Another reason why ground-level fighting on Earth is stupid for the Martians is that Earth has like 20 Billion inhabitants at that point, and Mars has "only" 5 Billion, and of course a lot less marines.
Though I have to say that most Sci-Fi universes, the Expanse being no exception, are overly optimistic about population growth, and they must have shipped at least hundreds of Millions of colonists to Mars to achieve the stated population. Earth alone will probably not reach above 11 Billion Humans.
This would be useful in the construction of an arcology. New York City is little more than 300 square miles in area. A single huge building could easily encompass living space for an even larger population than NYC's, while also offering domed parks. The aerogel would take care of the thermal and UV issues. There would have to be a strong transparent membrane, perhaps sustained by pressure, to withstand winds and protect the aerogel. Also, such a unitary building, with a dome structure around it, would be easier to protect against radiation with magnetic fields, as conductors in the dome itself could be used. Fusion power seems like a must have for this kind of project. Also, this would entail additional expense, which tunnel habitation wouldn't incur.
In the novel/TV series "The Expanse", Martians live underground in tunnels, because above ground it takes more material and energy to build air-tight buildings which also protect from radiation.
So perhaps such Martian arcologies would be playgrounds for the rich? Perhaps they would be the equivalent of today's Dubai?
And they still have adverse effects from the lower gravity.
One of the most fascinating aspects of that series is that there are three Human "subpopulations", two of which would have trouble to exist on Earth, physiologically.
We still don't know if the effects are necessarily adverse at Martian levels. There might be a benefit, so long as the radiation can be mitigated. In any case, the gravity could be mitigated with a "slanted racetrack" style centrifuge. An entire arcology could be constructed this way. It could well be that the residents of such arcologies would be stronger and healthier. That would be one hell of a form of class distinction. It would be similar to the combat differences between medieval Knights and peasant conscripts. Perhaps arcologies would become the castles of a warring Mars gone feudal?
[NB Those books seriously made me want to go to Mars when I read them - mind you I'd be a Red rather than a Green]
However, if the goal is the survival of the human species, I think we would be much better off by exploring the inside of our own planet first. I bet we could figure out how to safely live underground and harness the power of the Earth's core a lot faster than it will take us to make Mars habitable.
Earth is a gigantic spaceship traveling through space, and we are on the outside. Why not go inside the spaceship?
The frontier is in space, and every technological step we take towards that frontier is a step we can use to keep moving outwards.
That being said there's no reason both can't be attempted. One does not preclude the other.
"The frontier" is an arbitrary concept that we choose. We can choose another one.
We have limited time and limited resources, whatever we use for one thing we stop using for another. When the public mind is focusing on a big thing like space, it is not focusing (and reallocating enough resources) to another big thing like reaching the Earth's core.
I completely disagree with you here. Neither economies or governments (or "the public mind") are so completely focused and one dimensional as to only direct resources towards one endeavor.
The Apollo program didn't prevent the Soviets from drilling the borehole in the early 70's or Jacque Cousteau from exploring the oceans in the 60's.
I don't think it can be handwaved away, I think it's impossible outside of fanciful science fiction.
I'm sure that with enough time and effort we can figure out how to reach the Earth's core. Of course it will take a lot of creativity and lots of people and resources to figure it out, but we can definitely do it.
Also the Earth is right here, we are on it right now. Mars is very, very far away. We can iterate a lot faster here on Earth than anything we want to do on Mars.
What do we gain by colonizing Mars?
We can probably gain the same, or more, and faster, trying to reach the Earth's core first than trying to colonize Mars. In fact, reaching the Earth's core might even make it easier/faster to colonize Mars by applying all the knowledge and tech we would develop.
The deepest hole ever dug is not even to the mantle and is less than a foot wide. We could all live in a (modestly) deep cave no problem, but navigating lava is beyond the properties of any known material.
It's literally impossible to reach the core. No nanomaterials, no carbon nanotubules, no fusion reactors, no superalloys. I am 100% confident saying that human kind will never reach the center of the Earth.
The only reason why the Earth's core might seem out of reach to you is because of how little focus and resources have been put into it (compared to colonizing Mars).
> I am 100% confident saying that human kind will never reach the center of the Earth
Well, that is your own personal opinion. And in my personal opinion, it sounds very pessimistic.
We can definitely do it, and we might not even need to drill any holes. We just need to get excited about it and go for it.
On the topic of surviving extinction level events, it may very well be that researching how to live deep down indefinitely is a much better way to spend resources than researching how to survive Mars.
But for some reason you are arguing about going to the core -- which is so far beyond our current technology level that we may as well consider it scientifically impossible for now.
> -- which is so far beyond our current technology level that we may as well consider it scientifically impossible for now.
That's exactly it. Going to space or Mars, were impossible dreams for hundreds or thousands of years, now we have robots and satellites over there.
If we don't dream about going to the core, we will never get there. Big challenges make us dream big and work hard to accomplish them.
Also, despite now seeming so hard, I bet there's tons of low hanging fruit discoveries just waiting to happen. Have you seen a diagram of the inside of Earth? It's just laughable, especially if you compare that to the level of detail that we have of Earth's surface, or even the Martian surface.
Also having handled aerogel in the past, it has a very rough surface texture. I suspect it would quickly build up a layer of sand, negating the greenhouse effect.
The surface area of aerogel foam is huge and its ability to absorb heavy toxic metals from water is also huge.
I wonder if aerogel desalinization filters could be a thing.
I would have liked a discussion over how this stuff could be produced on Mars, because no self-respecting rocket engineer would allow transplanetary shipping of a material largely composed of air.
But yes, some kind of fission or fusion reactor would be on a colonization plan, if it is easier/cheaper than solar. One problem though would be getting fissile material. You can probably find some on Mars or its moons or some asteroids, but it would require lots of heavy industry to get enough of it for reactors.
Bringing significant amounts of nuclear fuel from Earth would be really unpopular, what with the risk of rockets blowing up. That risk or fear is also what prohibits the use of nuclear propulsion for space travel...
The bulk mass of a (normal) reactor is shielding and cooling plumbing. You don't need any shielding on Mars, and cooling could maybe (probably?) be some kind of radiator/convector to the surrounding air. Maybe you could even crack the CO2 with the heat directly?
Fusion needs a lot plumbing and containment. Fission is just basically a pile of fissile material in proximity. Not very hard if you can skip on all the protection.
You're right that, if you could find some useful endothermic reaction like vaporizing CO2, you could use it as a heat sink. The problem is that distributing heat to arbitrary places in the martian ground (remember, this CO2 is not magically flowing to you) requires an even more complex heat exchanger than that used by a simple earth-based reactor.
Not to mention that having no shielding would be hell for your robots; radiation hardening of automated systems remains non-trivial. But the fundamental thermodynamics strike me as harder.
Maybe there are niches where this would make sense, but the thermodynamics is the elephant in the room.
That's all for a typical high-power reactor setup. You can, of course, have a low-power setup with nuclear power. RTGs [1] use this approach, though they mainly rely on decay heat rather than self-sustaining reactions, which is just as well because they are also thermodynamically limited by the rate at which they can radiate heat away.
One addendum I should have noted: the efficiency of a thermal engine on mars would actually be perfectly reasonable for a small engine (it's nice and cold there, perfect for high efficiencies). The issue is that you can't dump the heat fast enough, so your heat sink will get hotter, trashing your efficiency and reducing your cooling capacity (both of which exert downward pressure on your final power output in a serious way).
[1] https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
Shielding on Mars could just be made from surface rock. or you bury the reactor in the first place. Radioactive waste (like the contaminated shielding) is probably a non-issue on Mars because there already is too much uninhabitable space anyway.
Anyway, such things are decades or centuries in the future. In the next decades, photovoltaic or other solar energy generation will rule on Mars.
[0]https://en.wikipedia.org/wiki/Depleted_uranium#Civilian_appl...
The main trick in making aerogel is drying it out, in a way when the liquid doesn't collapse the porous structure by its surface tension. Peeps on youtube usually do this through a "supercritical CO₂" process -- which basically avoids having any liquid surface.
That said, manufacturing aerogel on Mars seems way more feasible than transporting it.
(They also ran tests on aerogel pebbles, but don't talk about sealing questions for that form.)
https://www.nature.com/articles/s41550-019-0813-0
"The higher carbon dioxide partial pressure on Mars versus Earth is favourable for plant growth, but the low total atmospheric pressure means that at temperatures of 273 K or higher, the undersides of silica aerogel greenhouse shields would need to remain slightly pressurized relative to the atmosphere to avoid loss of water vapour either vertically or laterally. This would place light demands on their structural properties, which could plausibly be met by interspersing the silica aerogel with thin layers of solid transparent material or via organic polymer reinforcement""
Which is why the video proposes floating cities. I agree with GP, Venus deserves more consideration.
However, the "habitable" space under the aerogel may mainly be used for agriculture or as a temporary working area for people in vacuum-proof suits. One thin sheet of aerogel also sounds like a flimsy way of keeping atmospheric pressure.
Or do you really need a hot iron core?
I'd further guess that it would be easier to do the same with some sort of electromagnetic field. To enclose the whole planet would also be a giganteous undertaking. Much easier would be local field generators on the surface, maybe powered by a fusion generator.
At best this would be centuries in the future, at worst this doesn't make sense at all because it would require less energy/resources to construct huge greenhouses/domes that achieve the same thing and more.
The more immediate obstacles to colonizing Mars seem to be getting there in the first place, getting enough stuff there on a permanent/continuing basis for a few dozen people to live there for a few years, including radiation shielding.
It would be a really long time until there is a financially self-sustaining "colony", let alone one that can produce all of its own foods and much of its own technology and other resources. I figure it will be centuries until people even think about anything terraforming-related seriously.
Such a project would be achievable in the near future. I think we don't quite have sufficiently strong magnets yet, and it wouldn't be cheap.
The mass required is prodigious, but the energy requirements would be surprisingly small. The magnetic field of Earth above the surface stores about 100 megatons of magnetic energy; on Mars, and if the field were a bit weak, the energy needed would be much less.
Mars is smaller, and so the volume of the magnetic field would be smaller, and a lower field is probably enough. Since stored energy goes as B^2, maybe this energy could be reduced by two orders of magnitude.
Now your cloud city has to both float and be impervious to the sulfuric acid in that atmosphere. The best material I could using [2] was coated on smooth, uncorroded steel (making uncorroded steel on the surface is going to be a trick with all that sulfuric acid, you'll need a clean room just to make your steel). Steel isn't exactly the most floaty stuff, so I think it's going to be a challenge to make your floating city surrounded by a steel coating. Glass is also relatively impervious to acid, so you could surround your city with glass, at least it would let the light in, but I think it will make the weight problem even worse, because glass isn't all that strong.
Compare to Mars: dig underground for radiation protection, and let the inside pressure provide the force to hold the shell in place.
[1] https://en.wikipedia.org/wiki/Atmosphere_of_Venus
[2] http://www.sulphuric-acid.com/TechManual/Materials/materials...
I'm all for manned exploration of Mars, I think the amount of science a team of humans can do during the necessary mission times (while waiting for the launch window for the quickest return) will be insane. Actually, the amount of science humans could do in a WEEK would likely generate more data, and more discoveries, than every probe and rover sent to Mars to date. I think the extreme risks to the crew, which may remove any reasonable hope for a good qualify of life upon return, and could result in fatal cancer, is absolutely worth the sacrifice as long as the crew is 100% volunteers that have adequately been explained the myriad of risks.
That said, as cool as it would be to colonize another planet, Mars just isn't going to realistically be it. Not until we are well on our way to being a Type II civilization (arguably we are still decades, at least, from being a Type I) but constructing something like O'Neill cylinders is far more realistic, as long as we can figure out asteroid mining (especially if we can automate it).
Currently it seems we're doing everything possible to avoid doing so... what's needed to stop that? Ensured that we measured everything possible there is now in its pristine condition?
Imho, put some organic stuff on it, e.g. some of the toughest lifeforms, it may be the most useful thing humanity does :D
Mars terraforming is hard and will require serious tech. At a minimum you would need to crash asteroids/comets rich in water and nitrogen into it. So I wouldn't really worry about the 7% atmospheric pressure limit, it's not going to be a constraint that matters.
That's 1/369th the mass of Deimos.
I vote that we stick with the current plan, which, as you may remember, is to send there Arnold Schwarzenegger with a full supply of blue pills, guns, and highly breakable glass windows, so that he can activate the alien reactor that will melt down the poles, change the sky color filters, and anoint him as the Martian Governator !
https://news.ycombinator.com/item?id=20451289
(As an interesting coincidence, I watched it yesterday - and for the first time in several decades !)
Sadly I'm becoming steadily more convinced that I know the answer.
The irony is, if humans dealt with reality on a rational basis we'd have far fewer of these sunny sci-fi articles, but a vastly better chance of them actually happening.