A material way to make Mars habitable(seas.harvard.edu)
seas.harvard.edu
A material way to make Mars habitable
https://www.seas.harvard.edu/news/2019/07/material-way-to-make-mars-habitable
99 comments
Also the marines train at 1G just in case they have to fight on Earth which makes an interesting detail
Yes, and Bobby Draper (a Martian marine) still can't deal with it when she finally does go to earth. In the novel she admits to herself that the Idea of Martian marines fighting on Earth is ridiculous.
I always figured if they actually had to do that, there'd be combat drugs handed out like candy and it wouldn't be that big of an issue.
I think that might only help if fighting was on the scale of hours to single digit days (and at the extreme end of that, there might be long lasting repercussions).
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.
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.
I don't think Mars and Earth would go to war because of the mutually assured destruction (kinetic weapons such as asteroids). More likely they would fight proxy wars for resources / control of moons etc. This is similar to how the US/USSR on Earth struggled for supremacy.
Spoiler alert: In "The Expanse" all of the above happens...
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.
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.
The article is looking strictly at plant survival ("could be made habitable to photosynthetic life"). For that, the "usable pressure" is much lower.
Yes, that would be one explanation.
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.
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.
Yup - they specifically talk about partial pressures of a few gasses as needing to be brought up. But holding in just the partial pressure of those two is a lot easier than holding in a full atmosphere of pressure.
I don't think it works that way. Plants generally also need oxygen, if only at night or relatively little. So we're basically up to Oxygen and CO2, and Nitrogen might not be entirely avoidable either depending on how the plants are supposed to get their Nitrogen. Water vapor will also be necessary or unavoidable...
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).
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).
Does it protect against other radiation than UV? Does it also seal a gaseous atmosphere at a usable pressure?
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?
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?
I found the Mars Trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson a very interesting, although of course, fictional account of the terraforming of Mars.
I started Red Mars. I love the setting and engineering but couldn't get through all the political intrigue.
I loved the first part of it but there was a time skip in there somewhere and I completely lost interest. I never finished it.
Didn't Kim Stanley Robinson's Mars trilogy include tent cities on Mars that used transparent aerogels for insulation?
[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]
[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]
Aerogels are mentioned in both Red and Green Mars - Mostly as pillars for the tents, but KSR mentions "airgels" (spelling in my copy) as an insulation layer in the tent material too.
That seems odd. With the large pressure difference support pillars seem unnecessary for tents. Why did they need such exotic support pillars?
In the book "tents" euphemistically refers to tenting that encloses small towns. Also the tent fabric was a multi-layered thing (one layer was to absorb some radiation). Imagine this is why supports were seen as necessary.
[deleted]
He wrote that as pressure increased due to terraforming projects, the tents needed more support.
There is no timeline or time estimates on the article about how long this would take.
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?
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?
While I agree with you for the most part, the technology developed to dig down and live underground would mostly only be applicable to digging down further.
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 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.
We might not need to dig at all if we can figure out how to navigate lava/magma (lava submarine?).
"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.
"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.
That is way outside of what is possible. The pressures and temperatures so far beyond what material science can cope with - the outer core is "liquid" - but just 100 miles down it's well beyond the melting point of aluminum (2000 deg F) and almost 1x10^6 psi. The outer core is 1800 miles down, 10,000 deg F, and 5x10^7 psi. Assuming you acquired unobtainium that would not collapse and/or melt under those conditions, you'd need a insulators and power sources that are probably also made of or powered by unobtainium.
I don't think it can be handwaved away, I think it's impossible outside of fanciful science fiction.
I don't think it can be handwaved away, I think it's impossible outside of fanciful science fiction.
Today, colonizing Mars is also "way outside of what is possible". It's all a matter of wanting to do it and then figuring out how to do it, one step at a time.
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.
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.
No, Mars is pretty easy. Materials are there, solar works as an energy source there, and it's just an extension of known tech. I bet if - for whatever reason it became an existential issue - humanity could have habitable base there inside of 10 years.
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 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.
Like I said, we are here, we can iterate infinitely faster in figuring things out here.
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.
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.
I don't understand why you are so insistent on getting to the core?
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.
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.
> I don't understand why you are so insistent on getting to the core?
> -- 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.
> -- 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.
[deleted]
> ... whatever we use for one thing we stop using for another.
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 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.
Sure, and what happened after the 60s and 70s with those things? Did any of those get or is getting the same attention or funding as space programs?
Cool concept, though solid sheets of silica aerogel are very difficult to manufacture.. I wonder how well this concept holds up with leakage between panels, or using the 'gravel' version of aerogel?
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.
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 full paper proposes using this for literal greenhouses - growing plants only. What matters there is partial pressures of CO2 (actually higher than on Earth), N2, and H2O. So the pressure differential would be relatively low, well within the structural limits of the aerogel as long as there's a sealant between sections.
(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""
(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""
I think parent means the layer of sand would block sunlight, thus negating the greenhouse effect.
We need a “foam” of areogel in a host substance to be viable. The odea being that we can host the aerogel in a substrate material which can withstand/accept the design limitations of the applicatioon environ and support the reasons why we want aerogel there...
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.
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 guess there are a lot details not explained in the article and much of them have come up in the research.
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.
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.
The primary components of Mars's crust are silicon and oxygen. The components of Silica Aerogel are .... silicon and oxygen.
Thank you, I didn't know that. Though the next question is how much energy you need to part the silicon and the oxygen and bring them back together to form the aerogel.
One nice thing which didn't automatically occur to me, is that a nuclear fission reactor on Mars would be comparatively cheap to build. You don't need any radiation shielding at all. Just walk away and turn it on. Have it produce methane and oxygen or electricity or both.
That would require really good automation. I think most nuclear reactors still require a lot of manual labor relatively close by.
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...
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...
Fortunately, a nuclear reactor isn't radioactive until the reactor is turned on. Enriched uranium on its own is hardly radioactive at all (U235 t1/2=~700Myears); depleted uranium has meaningful safe non-nuclear applications[0]. There are orders of magnitude more radioactivity in the RTGs already used on deep space missions. Those are very carefully protected, but the risks are deemed acceptable. So long as you don't turn your reactor on until you're well away from earth, I see very limited risk of exposure to the public, far less than from a RTG.
[0]https://en.wikipedia.org/wiki/Depleted_uranium#Civilian_appl...
[0]https://en.wikipedia.org/wiki/Depleted_uranium#Civilian_appl...
Yeah... politically it would be hard, I agree. But I don't think it would be a show stopper technically to bring fissile material from earth. For one, automated nuclear power plants are being designed for use on here on Earth. The fissile material itself does not weigh very much. It's also not (very) radioactive until you start the process.
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.
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 still need a heat sink of some sort to extract usable energy from any reactor, nuclear or otherwise; this is a universal property of engines [1]. Radiators are very inefficient for this and would be far heavier than the equivalent water cooling method. Same for air-cooling (especially in mars's thinner atmosphere). The cooling systems are not just there to prevent meltdowns; you need heat to flow, in large quantities, from a hot place to a cool place in order to extract energy.
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.
[1] https://en.wikipedia.org/wiki/Thermal_efficiency
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.
[1] https://en.wikipedia.org/wiki/Thermal_efficiency
The low atmospheric pressure doesn't really affect the cooling because it could be compressed arbitrarily.
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.
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.
Actually, the CO2 is flowing, it's in the atmosphere. :) But maybe it's not enough.
Right, that's the point! The low pressure would make it very very inefficient, and you would actually need a heat exchange system far larger than earth reactors. We use liquid cooling in our PCs because a smaller heat sink can pump out more heat if it's going into liquid (for a fixed flow rate). This is why liquid cooling for CPU/GPU setups is quiet and effective: the liquid flows quietly and carries heat to a BIG, slow fan. Your fan and heat sink would be even bigger/faster at Mars atmospheric densities just to cool your puny CPU. Doing that at scale with no water cooling for your reactor would be absurdly materials intensive.
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...
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...
I was thinking about cracking CO2 into methane and oxygen - in that case you would need a high temperature. But I get the general drift - no good cooling. Maybe on could be plunked into the ice cap. You would need a lot of plumbing then though...
Ah, yes, that would be one good place to put a lot of the energy (if you could also get some water for the hydrogen).
If you ever heard of "liquid glass", or silica glue -- it's the same kind of material as in airogel, a mix of (hydrated) silicate minerals.
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.
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.
I wish we would focus on Venus. It have similar gravity to Earth's. There is an excellent video about it https://www.youtube.com/watch?v=gJ5KV3rzuag.
The atmospheric pressure and temperature on Venus are far too high for it to be habitable. Even if those problems were surmountable, there is no liquid water, and the days are very very long.
> The atmospheric pressure and temperature on Venus are far too high for it to be habitable.
Which is why the video proposes floating cities. I agree with GP, Venus deserves more consideration.
Which is why the video proposes floating cities. I agree with GP, Venus deserves more consideration.
If an atmosphere were created one way or another on Mars, would it not be stripped away again by solar winds? I thought the lack of a magnetic field is the reason why Mars has so little atmosphere left.
Yes, but it's very slow for human lifetimes; it would take millions of years
https://en.m.wikipedia.org/wiki/Atmospheric_escape#Mars
https://en.m.wikipedia.org/wiki/Atmospheric_escape#Mars
A more problematic consequence of the lack of magnetic fields is that Mars is not protected from cosmic radiation.
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.
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.
Can we give Mars a magnetic field? Crash a million iron-rich asteriods on it, and magnetize them?
Or do you really need a hot iron core?
Or do you really need a hot iron core?
The most viable proposal so far is to place a strong electro magnet on the Lagrange point between Mars and the sun. If sized correctly this acts as a radiation shield similar to a planet's magnetic field, with the restriction that it only works for radiation from the direction of the sun (which is the overwhelming majority).
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.
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.
I'm really no expert. I guess the iron core of the earth is too big to be feasibly replaced by asteroids "crashing" on mars.
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.
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.
One could run superconducting cables around the planet.
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.
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.
Were you thinking 100 MJ perhaps (which seems awfully low). Energy isn't normally measured in tons. But if you were applying e = mc^2, then that would be 8.988e21 MJ [1], which is a considerable amount of energy.
[1] https://www.omnicalculator.com/physics/emc2
[1] https://www.omnicalculator.com/physics/emc2
The energy stored in the part of the Earth's magnetic field above the surface is about the same as the yield of a 100 megaton nuclear bomb. This is about 4e17 J, or about 13 gigawatt-years.
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.
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.
You may be interested in watching The Planets (2019). It's a entertaining summary of space exploration/theories of the last two decades, and it talks about Mars and Venus (including the atmospheric loss theory on Mars versus Venus retaining an atmosphere) for an episode.
Thinking back to a comment I read on HN months ago, while this adds up over a few millennia, it is actually rather insignificant on an annual basis and therefore easy to counter.
Yes but that happens over tens, hundreds, thousands, millions of years. It may be practical one day to stay ahead of it.
yes but it takes millions of years so no need to worry, and the replacement rate you need is small.
Floating Cloud cities on Venus makes more sense. 1g, 1atm, habitable temperature, endless CO2. We'd need Oxygen and Water but that's true on Mars too.
https://en.wikipedia.org/wiki/Colonization_of_Venus
https://en.wikipedia.org/wiki/Colonization_of_Venus
Venus makes even less sense than Mars. At least on Mars once you get there is no barrier to mining what you need. But on Venus you either have to haul all your materials there, or be able to deal with the pressure of 93 atmospheres at temperatures of 900 deg F just to mine stuff. Plus all that sulfuric acid, which at 900 deg F is going to be highly reactive. [1]
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...
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...
Oxygen and water exist in ample supply on Mars - not at all on Venus.
An even better title would have been "Aerogel could be the material to make Mars habitable". And to be clear, I'm referring to the title on the article itself, not how it has been submitted here on HN :)
I think "material" as used in the existing title is a bit of a pithy joke (maybe in the spirit of the journalistic tradition of crafting cheesy titles). Your suggestion is certainly clearer, but maybe at the expense of being less amusing.
The full paper is freely available at https://www.nature.com/articles/s41550-019-0813-0
Doesn't solve the fact that there just isn't enough material to heat (ice and rock) to create enough of an atmosphere for decent pressure without importing massive amounts via asteroids.
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).
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).
How long before we'll put some organic material on 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
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
The problem is how do we know whether or not Mars already has life on it? If we contaminate it with our own microbes, we may mistakenly claim Mars had its own microbes to begin with.
At some point we will need to say "who cares". You can't possibly prove the non-existence of life on Mars. So at some point you need to stop looking and get on with things. When is that point? I dont know. My opinion is we should get humans there to have a look and then move forward - assuming they find nothing.
Supposed we are able to absolutely confirm or deny the presence of life on Mars which didn't originate from contamination by us. What problem(s) would that solve? That panspermia is possible? Would that need outweigh the need to discover how to make life survive outside of Earth? Would that not also prove panspermia is possible?
What if Mars is already inhabited? Do we preserve the existing life, or reshape Mars to our own ends?
This wouldn't be robust over the long term, which is the main advantage of going down into a gravity well rather than colonizing asteroids and open space.
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.
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.
Can you tell me about the long term problems that colonizing asteroids entails? It feels to me that colonizing the surface of planets is very wasteful: the entire core is rich of various elements which you could access if you disassembled the planet (there is no other way than disassembling it).
For reference purposes, a shell of [evacuated] silica aerogel exactly 3 cm thick, around the entire planet, is about 4e12 m^3 and 4e12 kg.
That's 1/369th the mass of Deimos.
That's 1/369th the mass of Deimos.
Such a shell would not be stable and would crash into the planet almost immediately without a huge control system to keep it in place
Of course you put supports under it. The point is the low amount of mass required.
You just have to build another shield volcano antipodal to Olympus Mons.~
Pff, aerogel greenhouses, that's soft !
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 !
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 !
I love it. No gerrymandering on Mars!
I think covering the thing in a few layers of plastic domes will be much easier
This reminds me of the Arnold Schwarzenegger movie Total Recall.
;)
https://news.ycombinator.com/item?id=20451289
(As an interesting coincidence, I watched it yesterday - and for the first time in several decades !)
https://news.ycombinator.com/item?id=20451289
(As an interesting coincidence, I watched it yesterday - and for the first time in several decades !)
but will environmentalist let us?
How about we stop wrecking the terrestrial ecosystem then worry about making other places habitable.
Apart from the fact that humanity can think about more than one thing at a time, thinking about this stuff will probably give us ideas for how to (counter)terraform earth.
I don't know about your 2nd point but to your first, I fear that though it's true, it is not an as well but an instead; we're thinking about other things so as to block out what we face now.
Agreed, the amount of resources, time and technology required to save this planet are minuscule compared to terraforming a distant inhospitable place.
Not sure why you are being downvoted. It's sad to say, but we are not going to terraform Mars. Why? Because that requires organized human life on earth first and the way we are going, it's a real question whether we will maintain civilization.
> it's a real question whether we will maintain civilization
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.
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.
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.