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For above-ground settlement I think what at least some of us are looking for is a Quonset hut.
https://en.wikipedia.org/wiki/Quonset_hut
The semicircular cross-section makes it an appropriate pressure vessel (although the flat sides might be somewhat problematic), and its lightweight material should make it rather cheap and quick for a theoretical boomtown to make. They can also last pretty long: many are still in usable condition 70 years after WW2. The main drawback I can find is poor radiation protection: new galvanized steel has an albedo of 0.35 (http://files.pvsyst.com/help/albedo.htm) and dirty steel has one of 0.08, less than even grass. However, if it doesn't adequately protect its inhabitants we could always put regolith on it as Oldfart1939 has so often suggested.
Could anyone provide me a schematic/diagram for Lake Matthew Team's Omaha Field proposal, or a link to it? I've seen its claimed power requirements and energy-blocking capacity, but I'd like to be able to see a diagram of its circuitry and power sources if possible. Thanks!
NOTE: I noticed and read Josh's link to Wikipedia right after I finished this but before I posted it. After reviewing it this might still be valid as it attempts to describe a pressured stress from one side of the membrane/wall/roof to the other, perpendicular to both σx and σy in the relevant Wikipedia diagram. Apologies in advance if such a thing turns out to be invalid.
Continuing on my previous work and hoping to generalize it, here's an equation for the acceleration of a parcel of fluid due to a pressure gradient from https://courses.eas.ualberta.ca/eas570/pgf.pdf with adapted notation:
a(P)=-∇P/ρ
Where ∇P is the magnitude of the greatest pressure increase at a given point (the so-called pressure gradient, something which might require multivariable calculus to determine but as shown below doesn't in this case) and ρ is the density of the fluid. The negative sign is because fluids want to move from high to low pressure, and thus follow the greatest pressure DECREASE and oppose the gradient. In any case we don't care about that since we're concerned with magnitude and not direction, so taking it out nets:
|a(P)|=∇P/ρ
The keen eye would note that this is an acceleration and we're looking for a force (and eventually pressure, somewhat ironically). Henceforth referring only to scalars, force is acceleration times mass, so we'll need mass. Density is mass over volume, so the mass of a gas is its volume times its density. Taking V for volume we get
F(P)=V∇P
We want a pressure from this, so we take this and divide it by the surface area that's exposed to the Martian atmosphere (so including the walls and roof, but excluding the floor). Giving that as S we get:
p(P)=V∇P/S=V/S*∇P
So we want buildings with low volume to surface area ratios, or equivalently high surface area to volume ratios. According to Wikipedia tetrahedra and cubes have the highest such ratios although that doesn't account for taking out the floor.
The tricky part would in theory be determining ∇P, but for any given piece of wall or roof the air would want to escape to the outside perpendicularly, as that would be the shortest way out. This "collapses" the ∇P into a single-variable derivative relating the change of pressure over the change of distance (i.e., the wall/roof thickness), which change we can assume to be linear (and thus derivative constant). Given internal pressure P and wall/roof thickness t (assuming that it is in fact homogeneous), and assuming the Martian outside is a vacuum, this whole thing simplifies to:
p(P)=V/S*P/t
Hey Josh,
Thanks for your commentary. I neglected the tension within the brick wall and only focused on the pressure gradient that was perpendicular to the wall. The acceleration due to the pressure gradient is given by https://www.shodor.org/os411/courses/_m … index.html (I didn't use the calculator, just its equation), and I essentially saw the wall as simply a way to increase the distance between the inside and outside and thus reduce the gradient to acceptable levels. The 2 psi figure I got from page 10 because I mistakenly thought that is what transverse load meant, but that was essentially my method.
Given that mistake and your inclusion of tension I believe your number is more reasonable, but we do ultimately agree that brick is garbage for exterior walls. If we really wanted it for aesthetic reasons, I would suggest we make a load-bearing wall out of a much better material and contain all pressure within it, and then lay the brick facade immediately outside it where there's no pressure gradient.
I would assume that a Martian building would likely contain around 1 atm of pressure (101,325 Pa, by definition) in order to best simulate Terran conditions. In imperial units this translates to ~14.7 psi, rounded up to 15 for safety.
According to https://www.gpo.gov/fdsys/pkg/GOVPUB-C1 … b23c4d.pdf, a brick wall with high-bond mortar and no vertical load can at best withstand 2 psi, and really more like 1.5 (and even vertical loads up to 150,000 lb don't let it reach 7). So a tenth of what would be needed. The force in question is the pressure gradient force, which depends on the change of pressure over the change in distance. If we really really wanted to make brick walls above ground on Mars, we would increase the distance between the 1 atm interior and the very low pressure environment, which in practice would mean increasing the thickness of the wall.
Assuming for both safety and simplicity that the Martian atmosphere is a vacuum at 0 atm/Pa/bar/psi/etc., and that the density of the air is the same as on Earth (1.2 kg/m^3), the magnitude of the acceleration due to the force using SI units is (101,325/1.2*thickness). Since I'm ultimately trying to get a pressure from an acceleration, I make up a couple of figures, but I hope they are somewhat reasonable. We need a mass of air to get a force; assuming a Martian brick building is around 100 m^3 in volume, this would give 120 kg of air, so the total force in N is thus (10,132,500/thickness). I assume that the height of the building is 5 m, leaving 20 m^2 for floor area. For a cylindrical building this gives an ~80 m^2 wall area (I'm neglecting the roof); doing the same for a square yields 25 m^2 for wall area. Pressure is Force/Area, so for the cylindrical building this gives (126,656.25/thickness) and (405,300/thickness) for the pressure. Maximum value was around 1.5 psi, but I'm going for a factor of safety of 2 so will thus cut the maximum pressure to 0.75 psi, which is ~5,175 Pa. This yields a minimum thickness of 24.5m for a circular building and 78.5m for a square building.
GW said that using published maximum strengths is a bit naive, which wouldn't surprise me. But even with such naivete it becomes apparent that a brick wall above the ground would not be feasible.
^Agreed, good luck with your back!
I think the definitive calling card for life on Mars, extant or otherwise, would be a depletion of Carbon 13 in sediment deposits. Life is ultimately just a series of self-sustaining redox reactions (which may or may not use Oxygen) that prefer to use Carbon 12 rather than Carbon 13. Significant depletion of Carbon 13 usually means either methane (which naturally has less Carbon 13 for reasons I don't understand) or life. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1664679/ gives hope with its rocks being found to be quite 13C depleted, but those are from meteorites and should be taken with a grain of salt.
I graduated from high school 2.5 years ago, Class of 2015. I already keep in touch with good friends in this age of social media (EDIT: And I meet up with them at least once every year), I don't particularly think I'd attend mine.
Whether "exposure" matters depends on the nature of the life itself. If it's completely foreign by the standards of Earth life it would probably be treated by the immune system as an abiotic infection and be no more or less virulent. On the other hand, if it's like bacteria some precautions should be taken but it shouldn't be too bad: fewer than 100 bacterial species cause disease in humans, compared to the 1000s in the human digestive system alone. The greatest danger would probably be if they're akin to viruses, but that is highly variable. I am of the opinion that if indigenous life is found it should be incorporated into any terraformation scheme, but that's just me.
Yeah, that's a plausible start. Not to get too off-track, but there are these wonderfully-preserved embryos from right before the Cambrian, around 600 million years ago: https://en.wikipedia.org/wiki/Doushantuo_Formation.
With respect to Mars, if Martian life is/was indeed related to Earth life, it would have had to exist around 3.8-3.5 billion years ago (around the time of LUCA on Earth), which Void says is plausible.
As an evolutionary biology major, I'm most convinced by the "ring of life" theory in which all Eukaryotes, rather than constituting a third domain separate from Bacteria and Archaea, are descended from a single archaeal host cell subsuming a bacterium to be its mitochondrion in a process known as endosymbiosis. This was a mutually beneficial process in that the host cell would give the proto-mitochondrion protection from predators and the proto-mitochondrion in turn would make energy for the host cell. Photosynthetic eukaryotes (i.e., plants, algae, etc.) took this process further, subsuming a cyanobacterium to be a chloroplast, and some algae subsuming even other entire eukaryotes for different levels of endosymbiosis. There are admittedly still some kinks to be worked out; we still don't know how or when exactly the proto-eukaryote developed a cell nucleus and other organelles, and an organelleless eukaryotic cell doesn't exactly match an archaeon, but given the various lines of evidence I believe it is the best model at the moment. It's not entirely certain when this endosymbiosis happened, but consensus places it at around 2 Ga, so I doubt that a similar event would have happened on Mars (at least one related to the Terran event).
This endosymbiosis would pave the way for organisms to outright consume food particles as opposed to relying on dissolved nutrients like prokaryotes, giving a predator-prey relationship and provoking an arms race. It would also allow for colonies of different types of cells to develop, like a reef, and such types of cells become increasingly specialized to the point where they stop being individual organisms and become part of a single multi-cellular organism (this can happen in prokaryotes as well, albeit very rarely). These factors would eventually (as in one and a half billion years later) produce complex macroscopic (and eventually quite massive) life at the beginning of the Cambrian period, and the rest is (geologic) history.
Viruses are still a bit of a mystery for biology, but if I'm not mistaken the consensus is that they were formerly parts of full cells that broke off on evolved on their own, albeit parasitically, many many times independently throughout the eons. If this is true then it is yet another deviation from a clean branching tree model of LUCA, as is the prevalence of horizontal gene transfer, but I don't think any of that outright refutes the concept of a last universal common ancestor, just makes it a bit more complicated.
Not sure if this is the right thread, but construction materials are also important. The regolith provides a practically unlimited supply of bricks for external walls. Apparently there are also calcium-rich veins on Mars https://www.nasa.gov/mission_pages/msl/ … 16615.html, which can be mined to make various sorts of plasters, limes, and drywalls.
For a generic term "Martian" works just fine for me, although some of the names provided in this thread might work for specific mission callsigns in the same vein as Gemini or Apollo. On the other hand, someone/something from Earth is a bit trickier, "Earthling" being too science fictiony, but I ultimately think "Terran" is the best idea.
Milk isn't particularly necessary for early Martians; indeed, the majority of the world's population is lactose intolerant, and spinach and kale are adequate sources of calcium.
The coolant in such a system must not freeze at the lowest temperature it could possibly face.
Water has the odd tendency to have its freezing point DECREASE with increasing pressure. So in theory we could pressurize the pipes to stave off freezing, but that seems a bit dangerous, especially since we'd have to lower the freezing point to a whopping -150C. We can use a different liquid, but very few materials are liquid at both -150C and room temperature, thought that might not be relevant so long as it's never a solid. We can also see how much the regolith would shield the pipes from such temperature extremes.
I calculated some nutritional values for crops per area needed to grow and the length of the growing season from my data in Post #504 and various sources from the internet. For the length of the growing season the day/sol distinction is irrelevant. Each list is in order from most efficient to least efficient. Crops marked by an asterisk in the fat list use C3 photosynthesis, which means that they can likely be made even more efficient with high CO2 levels in the greenhouse.
FAT:
Olives (via Olive Oil): 3947.4-9868.4 g/acre-day
Peanuts: 5299 g/acre-day*
California Avocados: 846.3 g/acre-day*
Florida Avocados: 558.3 g/acre-day*
Potatoes: 110.2-470.5 g/acre-day*
Quinoa: 83.6-193.6 g/acre-day*
Corn/Maize: 85.9-153.6 g/acre-day
CARBOHYDRATES:
Potatoes: 18583-79318 g/acre-day
Corn/Maize: 1460.7-2611.2 g/acre-day
Peanuts: 1766 g/acre-day
Quinoa: 993.5-2300 g/acre-day
California Avocados: 483.6 g/acre-day
Florida Avocados: 126 g/acre-day
PROTEIN:
Potatoes: 2280-9730 g/acre-day
Peanuts: 2797 g/acre-day
Quinoa: 188.7-436.8 g/acre-day
Florida Avocados: 126 g/acre-day
Corn/Maize: 85.9-153.6 g/acre-day
California Avocados: 108.8 g/acre-day
ENERGY:
Average solar radiation: 590 W/m^2 = 50.7 million kcal/acre-sol (theoretical maximum)
Potatoes: 84174-359274 kcal/acre-day
Corn/Maize: 6616-11827 kcal/acre-day
California Avocados: 9148 kcal/acre-day
Quinoa: 5395-12488 kcal/acre-day
Florida Avocados: 6552 kcal/acre-day
Does America not have adverse possession? If they've lived there for a certain length of time, can't they apply for deeds?
I believe that one of the requirements of adverse possession is that the true owners should be able to know about the occupancy and be proven to have done nothing about it, which isn't particularly likely.
You need to bear in mind that a 73kg mass weighs about 716 N on Earth but only about 272 N on Mars. The inertia of the body and it's parts remains the same as on earth. This will affect the work rate of the skeletal muscles, which will be much reduced relative to the same muscles in Earth gravity.
That is a good point, I assumed that it was only the mass that mattered. This negative impact on muscles makes protein all the more important. It is somewhat unfortunate that the most efficient protein sources are from animals, but I think early Martians can make do with such sources as tofu.
A deverse crop will be needed by man once we have gone a couple times as we will want to grow the population that is there on mars to allow for a greater independance from earths very expensive supply trains.
I agree, especially for nutritional purposes as I explain below.
Brought up earlier in this thread is what the dietary needs of Martians would be, in terms of protein, carbs, and fat. I am not a dietitian by any means and pulled all of this information from the internet, but I have decided to crunch some numbers. I think I've touched on this before in this thread with the calories needed, but I don't think I actually investigated where these calories came from, feel free to correct me if I'm wrong.
I assume a male Martian would be 160 lb (73 kg) in weight, 6 feet tall from the low Martian gravity, and have 15% body fat. (The validity of this figure can be debated in the Crewmember size thread, and if it turns out this entire post belongs there as well feel free to move it.) Giving this and assuming that they all are 25 (Earth) years old and all participate in moderate exercise gives a Total Daily Energy Expenditure of 2639 calories/day according to https://tdeecalculator.net/, which I'll round up to 2650. According to https://wa.kaiserpermanente.org/healthA … ncing.html, about 50-60% of calories should be from carbs, about 30% from fat, and 12-20% protein, although https://www.healthline.com/nutrition/ho … in-per-day recommends up to 30% from protein, which I'll take to prevent muscle wasting, which would likely affect early Martians.
This means a Martian man should eat per day 1325-1590 calories of carbs, 795 calories of fat, and anywhere from 318 to 795 calories of protein. Using their respective caloric densities via https://my.clevelandclinic.org/health/a … d-calories, this translate to 331.25-397.5g of carbs a day, 88.3g of fat, and 79.5-198.75g of protein a day. Taking the high values of all of these this means the Martian diet would need up to 684.6g of food a day (1.5 lb), around 0.9% of total body mass.
Doing the same for a woman (assuming a weight of 140 lb (64 kg), a height of 5'7, and 25% body fat, but keeping the rest the same) yields a TDEE of 2168 calories a day, being rounded up to 2200. Doing all the same math yields 275-330g of carbs, 73.3g of fat, and 66-165g of protein, a high total of 568.3g of food a day (1.25 lb), again around 0.9% of total body mass.
Taking only the male values and rounding up the highest amounts, I get 400g of carbs, 90g of fat, and 200g of protein needed. No single food item I know of has that exact ratio of macronutrients. According to various sources, mostly fatsecret.com and Google, here are some vegan items with various measurements of their macronutrients for reference. This is just a basic list for now:
Apple (per 1 medium): 19.06g carbs, 0.23g fat, 0.36g protein, 72 calories
Avocado (per 1 California avocado, weighing 136g): 12g carbs, 21g fat, 2.7g protein, 227 calories
Avocado (per 1 Florida avocado, weighing 304g): 24g carbs, 31g fat, 7g protein, 364 calories
Banana (per 1 medium): 26.95g carbs, 0.39g fat, 1.29g protein, 105 calories
Corn/Maize (per 1 ear, on the cob, cooked, plain): 17g carbs, 1g fat, 1g protein, 77 calories
Grits (per 1 cup, cooked, plain, not of the Justin Trudeau variety): 23.11g carbs, 0.34g fat, 2.56g protein, 109 calories
Lentils (per 1 cup, cooked, plain): 36.71g carbs, 13.25g fat, 13.25g protein, 323 calories
Oatmeal (per 1 cup, cooked, plain): 25.37g carbs, 2.39g fat, 6.06g protein, 145 calories
Potato (per 1 medium, roasted): 27.28g carbs, 9.52g fat, 3.16g protein, 203 calories
Potato (per 1 medium, baked, plain): 37.09g carbs, 0.22g fat, 4.55g protein, 168 calories
Quinoa (per 1 cup, cooked, plain): 42.17g carbs, 3.55g fat, 8.01g protein, 229 calories
Rice (per 1 cup, white, cooked): 44.08g carbs, 0.44g fat, 4.2g protein, 204 calories
Wheat bread (per 1 regular slice, plain): 12.26g carbs, 1.07g fat, 2.37g protein, 67 calories
Avocados have been mentioned on here before, and they are useful as a fat (and, depending on the cultivar, protein) source, especially in the days before mass livestock husbandry. According to http://edis.ifas.ufl.edu/fe837, one acre can produce 3,300 lb (1500 kg) of the stuff per Earth year, ultimately at a cost of $0.23/lb ($0.51/kg), although this figure does not account for greenhouse heating and importation. This efficiency can perhaps be increased, as avocado trees use C3 photosynthesis, becoming more efficient than C4 plants once CO2 concentration surpasses 700 microliters/L in the air, which can be pumped into the greenhouse.
The main drawbacks to avocados are that they aren't very adapted to the cold, requiring a minimum temperature of 20F (-6.66C) even for the hardiest cultivars, hindering production on Earth north of SoCal and Florida. Avocado fruit also browns very rapidly with air exposure from personal experience with guacamole, doing so within an hour, although that does not immediately affect its edibility. They're also hard to breed, requiring grafting, although the import of an initial "mother graft" shouldn't be too difficult. They're one of those fruits that require ethylene to fully ripen, like citrus, though that might not be an issue depending on the local chemistry. They reach a height of 15-20 feet at maturity, which would provide a minimum height of an orchard greenhouse and is similar to that of semi-dwarf and normal apple trees. Ultimately, I think growing avocados would be a good idea for Martians once a greenhouse for them is big enough and warm enough year-round.
Perhaps, depending on how warm the "deep sea"/mantle is. Methane melts at below 100K, so methane-using "photosynthesis" (albeit without light) could be feasible at such temperatures similar to how Terran organisms in the deep ocean use it. Perhaps the initial life on the planet evolved in such a fashion, and throughout the eons it evolved to be more accommodated to the even harsher surface of the planet similar to how you described it.
However, there is an important caveat. Most of the initial heat of planets, at least in the solar system, originates from the decay of 26Al, which has a half-life of 730k years, becoming "extinct" (i.e., below detection/ability to heat the planet) within the first millions of years of the planet's existence. However, you say that there has been tectonic activity after that point, which would stall the cooling off of the planet and provide heat necessary for life. You say that such activity is extinct on the planet, but perhaps the organisms on it have been able to take enough advantage of it while it lasted to perpetuate themselves.
Pretty much all life on Earth generates energy via redox reactions, which have the two advantages of being energetically favorable (in being both plausible and generating more energy) and being kinetically slow (so that energy doesn't get transferred/depleted too fast). I can't think of any other reaction type off the top of my head that also have both of these advantages (acid-base reactions don't give enough energy, any sort of nuclear process would give off energy too fast to be meaningfully used, etc.), so I'll assume that it'd be the same on this world.
Hydrogen can be used as an oxidant, as can Oxygen if also present. Oxygen is really good for redox reactions, being second only to the comparatively scarce Fluorine in electronegativity (tendency to gain electrons). The problem with Oxygen is that Oxygen and Hydrogen in the absence of any intervening force will almost certainly come together to form water, which freezes at temperatures well above 17K. I see two potential ways to overcome that barrier. The first would be to somehow "supercool" water, in which case it remains liquid below its freezing point. This can be done with the introduction of salt, but that doesn't work for temperatures below 0F (which is by definition the freezing point of brine). It can also be done in the absence of any seed that would initiate crystallization, but even that only works down to 220K or so. A more plausible way would be to use electrolysis to keep Oxygen and Hydrogen separate, like in a classroom experiment. A redox cycle to generate electrons, and then to use those electrons to keep Oxygen and Hydrogen separate, while using Oxygen to oxidize that which is desired, and so on, is somewhat feasible. However, Oxygen (according to Wikipedia) freezes at around 54 K, as do all of the elements other than Hydrogen and the noble gases, so Oxygen would have to be brought to that temperature by some means. Perhaps deep down closer to the heated mantle?
Progressivism is difficult to define; so many things have been attributed to "Progressivism" that it has become practicaly meaningless. But one key feature is the rich should pay more. That is, the more wealthy you are, the higher your tax rate.
Progressivism is a relative term. Prohibition and Eugenics were progressive movements in their time even if modern-day progressives would be opposed to if not outright disgusted at them. I think kbd512 can be forgiven for mixing up the various terms, as the Cold War's cultural legacy has prevented anyone from being nominally even socialist in the US and thus the term "liberal" has come to define pretty much anything left of center.
Yes, there are natural nuclear reactors. There's one in Canada right now, a mine that has the highest concentration of uranium ever discovered. No one has figured out how to mine it, because it's naturally reacting. It produces heat and neutron radiation. It's so radioactive that any miner would be killed. But it's still there, no explosion, no crater.
I thought Oklo was the only one known to have ever existed in Earth's history, but in any case the reactors are rare enough to preclude an explosion from having happened in the 4.5 billion years of Mars's existence. And even if there was an explosion, there would very likely be radiogenic glass from such explosion on the Martian surface, which has yet to be found (although in all fairness the rovers can only look for so much).
DNA need not be the nucleic acid of choice for Martian life. Even of Earth, a commonly-accepted theory posits that the earliest life had in fact RNA as its information-storage chemical. https://en.wikipedia.org/wiki/RNA_world
However, RNA does have the disadvantage of being less stable than DNA, especially on planet without atmospheric protection of solar radiation.