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I doubt this. Terrestrial rocky planets tend not to grow coeval moons, while the gas giants do with some uniformity. Mars has only 2 tiny captured asteroids. Mercury and Venus have nothing. Then Earth has this whopping big moon -- clearly an extraordinary situation demanding an extraordinary explanation.
Earth's hill sphere extends 1500 thousand km from the planet's center. That's a lot of room for a moon. Ours is only in the first 25% of it. Mars and Venus only have moderately smaller regions to form moons. There's no reason Venus couldn't hold an impact-formed moon, so your argument that it never had one would have to rely on finding a simpler, more likely explanation for its current rotational velocity.
The water vapor cloud bank just slowly departed further and further from the surface as it got hotter, this also got the clouds closer to the powerful UV to accelerate the process, free 02 and carbon became C02 and hydrogen leaked to space.
If we start with Earthly amounts of Water and Carbon we get pretty much what Venus is today.
I'm still going to disagree with this. If there were ever a significant amount of water on Venus, there should be a significant amount of molecular oxygen, yet there is none. The current CO2 is exactly the amount it should have. SO2 is a similar case. The complete lack of any oxygen on the planet does not lend itself to a large deposits of water that were lost to hydrogen photodisassociation. The Jovian moons have oxygen to show for this process. Earth has oxygen to show for this. Where is it on Venus?
It was never there. And that fits. The sun's early heat cleared it from that part of the solar system. For the same reason that Mercury is rich in high-density materials, and only received water from cometary impacts over billions of years, Venus should be much poorer in water than Earth.
Is this including the water trapped in H2SO4 molecules? ....
Yes it is including that.
I would like to hear your theory -- please go ahead!
The moon contorts Earth slightly, churning it up. Pretty reasonable. It's based on very well known tidal heating effects of other things. It's been touted that the formation of the moon prevented Earth's crust from having the same thickness as Venus's crust, which could be what is hindering Venus's interior cooling from forming a dynamo.
I would say that's probably right. Personally, I don't think a moon is really necessary for that. The geodynamo just requires a certain size and planetary composition. Getting the moon was just one way for Earth to arrive at that chemistry. But then again, I'm the crackpot who thinks Venus is easier to terraform than Mars. Well, maybe not easier, but the end product would be better.
Maybe he was talking about something else though. I don't know.
The default rotation would be tidally locked with the Sun. Collisions speed it up or slow it down.
Mars and Venus show evidence of large collisions in their past. Venus probably had a moon early in its formation, from something similar to Earth's moon-forming collision. Another collision of a similar magnitude resulted in its retrograde rotation, and this caused any moons formed before or after it to spiral into the surface.
I read an interesting theory that the slow rotation could actually be caused by friction with the atmosphere. It's significant enough to remove a substantial amount rotational energy from the planet. Along the same lines, the slow rotation could be caused by a resonance with Earth. One Earth occultation occurs every 5 Venusian days.
'Catching up' doesn't happen until the core solidifies, which may or may not have happened on Mercury. The real dynamo killer is a lack of convection. The interior is all the same temperature. Probably the case on Mars, and possibly on Venus. All fun things we'll get to find out about in a few years.
Venus is losing water, but it's losing water too quickly.
Ah hah! Now we're getting somewhere. Our difference is not the data, it's the conclusion. Venus is loosing water so fast that starting with similar water to Earth would have resulted in no water long ago, hundreds of millions of years ago. The reason there's water at all is attributed to new water released by volcanic outgassing.
You're concluding (or reading conclusions) that make a guess the magnetic field wasn't always this weak. But there's no evidence to support that. Mars, Venus, and Mercury all have very weak magnetic fields. Only Earth and the gas giants have strong magnetic fields. That has been attributed to our moon. I could give you my theory why our moon causes a strong magnetic field, but it's my idea. What has been accepted by scientists is simply that it does. The orther rocky planets in our solar system don't have a large moon, hence no strong magnetic field.
We can't really conclude anything about the past water based on current water.
It's very likely Venus had a magnetic field for most of its past. There are many competing explanations for why it doesn't have one now. Some guess there's no solid inner core, some guess everything's there but there are no currents due to the harder, colder nature of Venus's crust. That's probably the most compelling explanation, but if it were true, it would lead to a planet that was magnetized for most of its history, and still develops occasional pole moments with long periods in between.
Sure the moon helps, but is not essential. It wasn't a deal breaker for Venus. Mercury's 1% field flies straight in the face of that claim.
http://adsabs.harvard.edu/abs/1999Icar..141..226D
Venus is losing water, but it's losing water too quickly. The current water in the atmosphere is probably recent, because if most of it had been eliminated, there would be much more deuterium in it. Some more evidence for the intermittent periods of plate tectonics. The possibility is also brought up that it simply doesn't lose water this quickly most of the time.
Possibly a magnetic field that is simply undergoing a pole reversal right now? Or a field that has much longer dormant periods? I'd like to think that, but the prevailing attitude is that it had a strong earth-like field for the first billion years or so, and a gradually weaker field until 800 million years ago. http://www-ssc.igpp.ucla.edu/personnel/ … venus_mag/ this talks about that. Seems a field over much of its geological history would preclude your explanation for out-gassing. Though a dynamo is not going to stop the process of hydrogen loss. It happens on Earth.
That would be interesting news to find out, but we won't know that until we've studied the planet's internal structure more. Right now we only have fuzzy gravity data and inferences based on what a planet 'sort of like Earth' should act like.
What's more, the dirtiest of coal plants relesae large amounts of sulphur dioxide and dust into the atmosphere, which actively reduce global heating.
Can being the operative word, since these will still have a heating effect if they remain in the lower atmosphere. Ozone can also become a greenhouse gas when it's released from industrial processes and lingers in the lower atmosphere. Combined with its toxicity to organic systems, we generally consider it a pollutant when it's close to the ground.
Plus, y'know, mining coal has a whole bunch of environmental problems too. Mining natural gas is easy in comparison.
Put very eloquently, and if I didn't already know that the deuterium to hydrogen escape ratios didn't support your claim, I would probably agree with it. There are two models for outgassing that the Pioneer data supports, and neither is conclusive. It'll have to wait until the next barrage of probes to be resolved.
And no, Venus does not have more water than I think. Water is only .002% of the atmosphere, 18.6 kPa. A pitifully small amount compared to Earth's total hydrosphere.
I'm willing to bet it never had much water. That the current atmospheric level has been stable over long time periods, renewed through geological processes and comet deposits. The complete lack of any atmospheric oxygen would seem to support this. Stellar evolution predicts a lack of water. And the abundance of CO2 is better explained through other processes.
Water exists only in trace amounts in Venus's atmosphere. However, there's an awful lot of atmosphere, so the amount of water there could prove to be the proper amount a planet that close to the sun should have.
I'm banking on Venus never having enough water in the first place.
If it had Earthly amounts of water on it, where did it all go? Photodisassociation leaking hydrogen into space? If that were so, we'd see a lot more oxygen in the atmosphere, yet there is none. Plus, you would still see more water. Venus has 93% of Earth's escape velocity, so it does a pretty good job keeping water vapor from breaking up.
This explanation also seems to be a concession that there was always a thick atmosphere on Venus. If it were ever able to form standing oceans, it would become very difficult to destabilize the climate as it has been. Oceans act as a CO2 sink. Dissolved CO2 would be recycled into the mantle in areas where crust was subducted. Our most widely accepted model of Venus's geology shows tectonic plates completely renewing the surface in intervals every 500 million years.
Don't stop there. I didn't mean an alternative Earth. Just use Earth in place of Venus, to use what we know applied to "terraforming Venus." Would it even be feasible to sustain life with such a rotational configuration. (What could have caused it, by the way, and what a damn shame it turned out the way it did.)
It's difficult to say what the temperature of Earth would be in Venus's orbit. The most optimistic estimate I heard was 36 degrees Celsius. Uncomfortably hot but possible to live in. We might be able to artificially bring it down.
I would recommend looking at this site, as it does a good job explaining how all this temperature stuff works.
Note that the surface temperature of Venus without an atmosphere is not known. If the surface is 30% reflective, like Earth's, it would be around 25 degrees Celsius already, compared to Earth's -17. Earth's atmosphere adds 32 degrees to its temperature, bringing it to 15 degrees. Earth's atmosphere around Venus would then supposedly bring it up to 57 degrees.
I'm pretty sure 57 is the average temperature Nickname is using, when he talks about a boiling equator.
Make no mistake, a 57 degree planet would not be fun, though unlike Venus now it would actually be a plausible world to live on. Just build surface structures that create shade, and the area under them would instantly fall back to earth temperatures. An ecosystem could be engineered to survive this hot world. If this were the end-product of terraforming Venus, it would still be worth it.
This is probably not a correct estimate of Earth's temperature in Venus's orbit though, because it simply assumes that the amount of water in the atmosphere will be the same. Obviously, if you're hot enough to boil the oceans off, that's not going to happen. The extra heat would spread more atmospheric water into the upper atmosphere, forming a larger amount of cloud-cover, and reducing surface temperatures.
On top of that, an atmosphere with the same composition would be more reflective at higher temperatures, due to its changing specific heat.
These should bring the average surface temperatures down to around 36 degrees celsius, which is still quite hot, but good enough. This is what we're aiming for. This would be Earth in Venus's orbit.
The slower spin, lack of axial tilt, and thicker atmosphere (3 bars of Nitrogen) will all change Venus's temperature with respect to Earth's, probably lowering it some extent. Especially the slow rotation. All the clouds forming on the sun-facing side of the planet would not last long enough to insulate temperatures on the night side of the planet, making it significantly colder on that side than normal.
I would also raise questions as to just how much rock is present on the surfcaces of Ganymede and Callisto. Is there actually enough material there to form a significant crust? I was under the impression that the surfcae of both worlds was icy, with small amounts of rock and dust present from meteorite fragments.
If heated to Earth temperatures and pressures, they would have deep oceans covering the entire surface.
The visible surface is entirely rock, the belief that there's ice present is based on density calculated from gravity. In fact they don't have any direct evidence of ice on Ganymede or Callisto.
They have lots of evidence for large amounts of water on the moons: induced magnetic fields caused by deep oceans just under the crust, reacting with Jupiter's magnetic influence. These oceans would only be sustainable with pressure from massive icy crusts.
Much as you might protest, the gravity measurements really make it look like they're full of water. Other explanations for their lack of density are less likely. The decreasing density of the moons as you move further from Jupiter fits a pattern of Jupiter's early heat clearing volatiles from the interior of the system. The pattern of gravity from the moons indicates the separation of layers in their interiors by density, caused by Jupiter's tidal stresses. Callisto obviously is less differentiated due to its distance from the planet and other moons.
There could be something else causing this, but it's unlikely. The crusts are made of a combination of types of ice that form at low temperatures and pressures. Pressure beneath the crusts causes ice to form oceans. Pretty straightforward, and generally accepted as the scientific consensus.
Might I suggest simply adding water, up to a point, and letting photosynthetic bacteria fix the CO2 and H2O into organic compounds? Allow any excess oxygen to collect, so it will oxidize the crust at high temperatures, forming rust and salts and mostly taking care of itself.
If there's too much O2 left, THEN we consider eliminating it with imported hydrogen. I guess we could mine it from asteroids.
Don't forget that extra O2 is needed to dissolve in the oceans that form, and to form an ozone layer that's considerably thicker than Earth's. O2 is a bit of an anti-greenhouse gas; it'll push heat higher in the atmosphere than CO2.
So Venus has yet another vicious cycle working against us -- if the atmosphere cools enough to let heat escape, then the magnetosphere gets stronger and it retains its atmosphere more tightly against the solar wind, leading to reheating. It has reached equilibrium in this direction.
I'm not going to speculate about the magnetosphere. It does seem possible that removing the thick atmosphere will cause the planet's internal heat loss to speed up. Really, we'll know more about this stuff when the barrage of spacecraft studying Venus map its temperatures and internal structure better.
This shouldn't affect temperatures, so far as I know.
I've never been very keen on 'giant mirrors and lenses' in space. Where would the metal come from? How would you keep them from collapsing under their gravity? How would you keep them tidally locked to the body you're terraforming?
Just for the heck of it, does Jupiter emit a significant amount of infrared, by any chance? It'd be interesting if such a planet could be used as a makeshift star.
There is a big challenge here, how to be keeping space food equipment small, light and easy to maintain during a two-year Mars trip and without costs going out of control
I think this is more of a reflection on our lack of an adequate launching mechanism. We need some gigantic railguns. Surely the instantaneous electrical cost of these things would be less than the gradual cost of electrolyzing water for liquid fuel engines.
Putting heavier things in space would open a lot of doors.
No more seasons, for starters. Venus is not tilted significantly with relation to its orbital plane. Perhaps retrograde rotation would reverse atmospheric currents?
Not sure what it would do to the number of cells. Probably nothing; I think that's more affected by the rotational velocity of the planet. It would cause temperatures in each cell to become stable. Much less temperature discrepancy between day/night than a planet with a stronger tilt. Something I imagine would be very helpful for a planet with long days.
Actually I suppose Earth's orbit would have very small seasons, since it's not completely circular, and varies over time. They would just be global, and last irregularly throughout the year. Venus's orbit is the most circular of the inner planets, so it wouldn't have that.
Condition 1: Precise atmospheric composition.
Second, the Earth had to be large enough to hold a strong magnetic field and active geology for billions of years, yet small enough and outside of the star's hot zone to avoid accumulating a hot, dry, dense atmosphere like Venus, or excessive volcanism that would plague a larger than earth terrestial planet.
Condition 2: precise size and distance from star.
Condition 3: Jupiter. Without a massive planet at about the right distance from the sun, the Earth would be slammed by comets on a regular basis.
Condition 4: A large moon. Our moon is very large, compared to its planetary companion. Lunar is as large as the moons of jupiter, a planet 300 times as heavy, and it formed under very unique conditions. Without it, the Earth's axial tilt would be unstable and it would be subject to frequent and very intense climatic swings.
Condition 5: A stable star. Only 15% of stars are as stable as our sun, most exhibit much more intense and frequent flaring activity, that would lead to climatic swings and would compress most planetary magnetic fields, leading to steady errosion of planetary atmospheres.
These helped us become exactly like we are, but I doubt they're a necessity for complex, intelligent life. Just complex, intelligent life very similar to us.
For instance, a less stable star isn't so bad if it's really long lived. If we had been a few billion years late, we'd be cooked. A red dwarf that has trillions of years of life in it would be quite a luxury for any multi-cellular life to develop. Considering the amount of red dwarfs out there, it seems like a safe bet that they'll have most of the life we find.
Investments that take thousands of years to pay off, but keep paying for billions of years are very worthwhile.
What company or government do you expect to be around for those billions of years, so they could reap the rewards?
If reaping the rewards is going to take longer than you have, the amount of those rewards is irrelevant. A 120-year old guy isn't going to make a big investment that takes 100 years to pay off.
So rewards that pay off over a geological period of time are irrelevant economically to any entity engaging in them.
For the good of humanity then? For science? We're spending a significant amount of money researching fusion, and it's not going to pay off until late in our lifetimes, if at all. Much of this is a logical extension of the increasing scale that our economy operates on.
Of course human lifespans will increase too.
Really, your view of human reasoning is too narrow. We're completely capable of applying foresight beyond 100 years, and while there are short term reasons we could choose to not act on it, that would seem to defy our natural curiosity.
You're forgetting time. Investments that take thousands of years to pay off, but keep paying for billions of years are very worthwhile. What we're talking about is expensive, but there is no scarcity of resources to hinder it. Everything we need is right here in the solar system in abundance, and can be collected without straining our resources. Instead it becomes a function of the amount of time paying resources in, and the amount of time profiting from them.
When we talk about terraforming, we should be talking in terms of results, because the quality of those results reflects the cost a lot more heavily than the short term costs in getting them.
Venus and Mars can both be terraformed, no question of if. One of them will have enough gravity to walk normally on, enough to reproduce without possibly bad side effects, and enough geological activity to keep the surface rich in important minerals. One will be a lot more comfortable, but that doesn't rule the other one out. A lot of comfort can be lost before a planet becomes inhospitable. Neither would ever be as comfortable as Earth, certainly.
And neither will be terraformed in our lifetimes. It'll take probably thousands of years. It'll take hundreds of years just for us to get the economic strength to start. By the time we can even debate starting, we'll have a massive space economy, hundreds of times more capable of moving resources than our current one, automated, always advancing. At that point, terraforming simply becomes logical, as there's nothing else to do with the massive resources we can tap.
Terraforming Venus with algae/bacteria is a dead duck from the start. What are you going to do with the trillions of tonnes of carbon and oxygen within the atmosphere? And where do you plan to get sufficient hydrogen and mineral trace elements to sustain the bacteria?
Redirect dozens of comets to collide with Venus, transferring oceans worth of water. Water is in surplus in the outer solar system, and already in its natural form. Gaseous Nitrogen? Generally in other forms. Every time you have to convert something, unless you can do it organically you'll be doing it very expensively. Especially when you're forming N-N triple bonds.
Even if it were possible to reduce the carbon through organic processes, you would still be left with an atmosphere containing 60 bars of atomic oxygen and a mass of carbon sufficient to cover the planet to a depth of a hundred metres. Not an easy problem to solve.
The carbon layer drawback occurs with a different method of terraforming, where you import straight hydrogen instead of water. You can avoid making loads of atmospheric oxygen with this method, since it's all converted into water. I was interested in this method for a while, but it seems like importing straight water would be thousands of times easier, and extra oxygen is not necessarily a byproduct.
The only plausible solution as far as I can see would be to completely block out the sun from the planet, allow it to cool to cryogenic temperatures (beneath the freezing point of nitrogen) and then simply fire the solidified CO2 into space electromagnetically.
This is very implausible, and it'll kill the planet anyway. The CO2 is important. We want to convert it into glucose and ATP. If we want to build a stable C-O cycle, we have to build a large biomass, similar to the one on earth. Achieving this is complicated, but if sufficient water is present in the atmosphere, we can give it a good start with photosynthesizing bacteria, that'll fix the CO2 in useful solid configurations. Phosphates, nucleic acids, and carbohydrates require a lot of oxygen and carbon, sticking to aerobic bacteria should skirt the '60 bars of oxygen' problem. Slowly, all of the atmosphere will become fixed in solid form as a bacterial 'lawn'.
We also want a bit of an oxygen surplus, relative to earth. Anti-greenhouse gases like ozone will play an important role in reducing atmospheric temperatures, and a lot of this stuff needs to dissolve in the ocean the comet-water will eventually form.
It is uncertain who would want to undertake such a project and why. The cost of such large scale planetary engineering would be gigantic, the investment timescale measured in centuries or millenia, and unlike Mars, it would be impossible to terraform Venus in an easy and incremental way. If the solar system started running short of carbon in some distant point of the future, it might be possible to justify mining the Venusian atmosphere, with a potentially terraformed world as a long-distant side benefit.
From a financial viewpoint, it would be preferable to build a several thousand large O'Neill colonies, providing an equivelent surfcae area to Venus.
I don't think you've quite thought out Mars to this extent. Getting enough Nitrogen to it is just one of a series of painful steps that require extensive mining and refining. It certainly can be done, and we might even start the process sooner, filling the atmosphere with CFCs and hyper-greenhouse gases. I think that the calmer surface conditions on the planet have created the illusion that the planet is closer to Earth chemically and just a few short steps to terraform.
This is not true. Venus is chemically very close to Earth in the interior, and close on the exterior as well, but lacking one ingredient, water, because the Sun's early growth cleared it from the inner solar system, and all the inner planets. All the water that accumulated on them is thus the result of cometary impacts, which occur more often on planets further out, like Mars and Earth, and less on the inner-inner planets, whose orbits were rarely crossed.
The thick toxic atmosphere is simply the natural form of all the life, oceans, soil, and crust on earth, if you took all the water out of them. Chemically remove it from every molecule in every cell, pull it out of the rocks, you'll get CO2.
Achieving ecopeiosis on Mars will be complicated, and ironically it will involve making a thick CO2 atmosphere so photosynthesizing organisms will sequester it. Unless you have better ideas.
Given Venus's hostile environment, relatively deep gravity well and general lack of anything exceptional that it might export, I would anticipate that this will probably be a deadzone for future human colonization.
We have an entire other thread for this. Feel free to bring this up there, since you haven't yet. I've already spent a lot of time developing my case for Venus, and there's plenty more I haven't discussed yet.
Although if you want to talk about 'costing too much', you're on the wrong forum. Terraforming any planet is going to be incredibly expensive. We can't even imagine the costs properly. Every planet is a gravity well. Terraforming Mars at all would seem completely without economic merit, compared to mining all the low-gravity bodies, ignoring the neighboring planets, and calling it a day.
I think the purpose of any sort of floating base would be primarily for terraforming. Nothing manned would be needed. Just automated facilities that grow and release bacteria that can sequester the thick CO2 atmosphere.
I wonder if it would be possible to set up a base on Maxwell Mount's summit (tallest mountain on the planet). It would be subject to far less atmosphere than the lower areas. Depends on the temperature.
I don't really believe that manmade global warming is that big of a concern, and even if it is I'm not certain it's that bad of an idea. I mean I think it's too hot already so making it hotter doesn't really make me feel worse off.
I think the threat of tropical diseases in temperate regions and lower oxygen supply for fish stocks are pretty good reasons to try to avert global warming, though there are others.
It is true that Earth has been warmer for much of its history, indeed, it could have been warmer for most of its living history. Instead of interpreting this as a sign that it should be warmer, I rather see it as a sign that earth is most comfortable to humans at its early modern temperatures. Rapidly reverting to the hot climates that might have been ideal when all of the life on Earth was bacterial, or when dinosaurs were large and ferocious instead of little feathery things that Col. Sanders built a business off of cooking, doesn't seem to bode well to the established collection of species.
I would make the horrible, hippy treehugging socialist claim that rapidly heating up earth would destroy species variety and reduce the scientific interest and natural beauty of a lot of places on earth. This is pretty well certain.
We could debate the effect it would have on the economy all day.
The economy is a machine that makes certain types of decisions very well. It will make decisions that try to foster its growth. It will deal with arcane problems like carrying capacities and diminishing exotic biota on a reactive basis, as long as they don't harm its growth. Foresight only applies where growth can occur, to the limits that culture and scientific knowledge allow. Peak oil doesn't need to happen. Half the agricultural lands don't need to dry up. Major flooding and other economic arguments for averting global climate change don't need to happen. Chances are, the economy will be clever enough to deal with them anyway. It'll move people around, switch between resources, and advance itself out of harm's way. We have a very can-do attitude when it comes to surviving things.
Unfortunately the stuff we eat, breath, and admire in national parks doesn't seem to adjust on quite the same speed.
I'm pretty sure Venus would be easier to terraform than Mars. Seeing as it lacks water, which is cheap, and Mars lacks nitrogen, which is quite expensive.
And as for the moon thing, it's not so cut-and-dried. Earth's moon has no ocean, and no atmosphere. Titan has practically no sunlight. Ganymede and Europa lack atmospheres, and Callisto lacks internal geology. They all have their own problems.
One thing with Jupiter's moons is the deadly radiation - 10 minutes unshielded is enough to kill a human.
Europa is the worst off. Until you've got lots of well designed atmosphere, you're probably going to be living under the water.
You might want to think about Titan first. Saturn's local environment is relatively benign. Use large mirrors/Fresnel lenses to up your solar wattage.
I never really saw the appeal of Titan. The nitrogen atmosphere is about all it has going for it. It's too cold, too inert. Plus, it's a very pristine environment, with the 3-phases of hydrocarbons on the surface.
I'm going to have to agree that Callisto is probably the best candidate in the Jupiter system for colonization. It's far enough from Jupiter to reach fairly easily, without having to use a lot of fuel to get inside the steep gravity well that the other moons are in. Gets no radiation from the planet too.
Ganymede might be a better terraforming candidate for the long term. Not that it's that great of one to begin with. Radiation is not a problem there either. We'll see.
I regretfully say that it's unlikely anything in the outer solar system, even Jupiter's moons, can be terraformed. These cryogenic bodies receive a mere 3.5% of the sunlight we get on Earth, and while they have other redeeming qualities over Mars and Venus, when plants can't photosynthesize on the surface, you run into some huge sustainability problems.
This is unfortunate, since Ganymede in particular has pretty good credentials for holding a thick atmosphere. It produces its own magnetic field, which is enough to shield it from Jupiter's magnetic influence, which also shields it from the Sun's. If Ganymede, or Europa or Callisto for that matter, were terraformed, it would result in an ocean world, with hundreds of times the water depth of Earth. The variety of organisms that could thrive in a low-gravity water environment is staggering.
So here's a thought: what if the geological activity inside the moons is enough to sustain chemotrophic bacteria that can replace CO2 with O2? Building thick atmospheres aside, would it be possible to design an ecosystem off of this?
Interesting to think about, even if we decide it wouldn't be economic to try.
