Self replicating machines are one of the things I think both New Earths and Terraforming should have covered, but largely ignored. Though speculative, there are quite a few things we could say about them, both in capabilities and limits. Some of the key points:

- The key advantage of self-replicating machines is that (assuming sufficient inputs) they could provide rapid scaling of physical capability. So, things like (for example) planet diameter sunshades/power collectors wouldn't be out of the question.

- Self-replicating machine <> (doesn't equal) nanomachine. A self replicating machine might be the size of a factory with (relatively) large components, or the size of bacteria. On the other hand, nanomachines wouldn't necessarily replicate. Personally, I suspect we will have macro self replicating machines before the nanoscale kind.

- Self replicating machines can't break the laws of thermodynamics, transmute elements, and so on. They would still require energy and mass inputs, and there would still be limits to how fast certain things could happen (for instance, how fast the Venusian atmosphere could be cooled).

- They would need to be designed, programmed and overseen. A computer is great, but useless without software. To terraform a planet, there would need to be massive planning, software, and control. (It's conceivable that advanced AIs might eventually be able to do this on their own, but if they reach that level, you have to wonder why they would bother. Perhaps as a favor to their pets?)

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Good points. Not unlike Von Neumann machines in that they could function until they break (first under environmental strain) but then the worn out machine serves as raw material for succeeding self-replicating machines which also draw needed raw material or chemistry from the natural environment.

Pets. That would be us, yet we might also be sort of matching (or melding with) AI by that time. But that's another story.

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"Insignificant molehill sometimes more important than conspicuous mountain." - Charlie Chan

Great, then everyone will have one. Can you imagine all the people trying to have their nano-pea terraform venus at the same time with different ideas no how it should look? It'd be nano-warfare as each tried to re-terraform the neighboring nano-sites.

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

There might need to be some regulation to prevent that sort of thing. Or perhaps they will regard it as fun and the best nano-war wins a prize each month.

I think micro-organisms would be best to terraform Venus. They're basically tiny robots, that already possess self-replicating abilities. If you manipulate their DNA to make them more resistant against the harsh conditions on Venus, all you have to do is wait a couple of centuries.

Although you'd still probably get crushed by the atmospheric pressure or burn up. Or maybe your terraforming bugs mutate into flesh-eating microbes. Now there's a new horror-genre: Terraforming terror. "They used to eat carbon dioxide. Now they eat carbon-based life forms!"

This is probably based on Sagan's proposal, but I'm afraid it just won't work. Fogg covers this in some detail in Terraforming*. If you didn't have to worry about the resulting oxygen or carbon, had enough water and nutrients, and just considered sunlight, it would take an absolute minimum of about 570 years assuming 100% efficiency. Assuming 5% efficiency (incredibly high for plants) it would be over 11,000 years. Assuming a more realistic figure (.05%), it would be over a million years.

But, there isn't water, nutrients would be limited, and (assuming it actually worked) you would end up with 65 bars of oxygen and hundreds of meters of carbon on the surface. The results would be exciting . . . for a short time.

While Sagan originally proposed the algae idea, it was before we knew just how bad Venus really was. He later stated some of the issues with it, based on more recent information. It really was Adrian Berry and Jerry Pournelle that pushed the myth (and extended it, with it only taking a few rockets to convert Venus in a few years!). Pournelle later also acknowledged that it wasn't so easy. Ultimately, Venus would require intensive technological intervention.

*There is an extended discussion on terraforming Venus, but most of the points in this post are dealt with on page 354-355.

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

I know this thread is about terraforming, but would a sheltered dome be a better solution for colonisation? Lets say you bring all the materials from Earth, air-drop them on Venus and have robots (that can withstand the heat and pressure) assemble it on the surface. People can them come down in ships/special shuttles to dock with the base without exposing themselves to the atmosphere.

Would that be possible or am I underestimating the conditions?

Quick question here: I just read that Venus has a pressure of 90 Earth atmospheres. Will ships ever be able to take off after landing on Venus? Does a dense atmosphere means it behaves more like water (providing better lift when gaining altitude, like manouvering in water) or is it going to create so much downward force that your ship is stuck on that planet?

OSC, I'll respond later, but for now, you might get a kick out of this article on the idea of floating cities on Venus:

http://spacemonitor.blogspot.com/200...-on-venus.html

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Wow, great link!

So the atmosphere would behave at the surface as if you were 1 kilometer underwater. I figured that gas planets would provide bouyancy if you go deep enough into it, but I never thought our neigbour Venus could support floating cities as well.

The idea of a floating habitat high up in the atmosphere of Venus sounds great. You have twice the solarpower (PLUS the clouds reflect light back as well!), you can use the wind (and probably a few thrusters) to fly the habitat around in a 24 hour day/night cycle, collect raw materials , do research, and it's a fairly good jump-off point to reach asteroids to mine them. The upper layers of the atmosphere will block out harmfull solar radiation, while clouds beneath the station would reflect light back. (just summarising for those who don't want to read the whole article, although I can recommend it)

This also means you don't have to seed any micro-organisms into the clouds.

We could probably solve the pressure difficulty if it were not for the temperature difficulty. Venus should be "explored" from the top down. The sulfuric acid clouds are believed to be a source of water and the bottom of clouds are at or near temperatures and pressures commensurate with the Earth's surface. Balloon suspended modules operating just below the clouds with microbes like methanopyrus kandleri and its thermophylic friends, genetically modified to the extent necessary, will begin the automatic terraformation of Venus. We'll work on the H2SO4 clouds with some acidophylic psychrophiles hoping that removing the clouds will help Venus cool off some. Depending on how watered down the H2SO4 is, we may have to import some water to be used as a catalyst in the balloon suspended modules.

Assume that we are being tested by the information managers of the universe to see whether we have noticed how convenient the design of the solar system is for us to learn to become space faring.

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

So you think that in the end Venus should be terraformed with (modified) microbes? Personally I think that people (mining corporations, the government, the international board, etc) will terminate the cash flow once it has been mined and explored. It's a wasteland with some vulcanoes, and acidic rains. Quality real estate.

What were the predictions again? Wouldn't it take something like 10.000 years to transform Venus into something habitable by terraforming? I'll stick with flying cities in the clouds.

Biological methods simply are insufficient to terraform Venus. It won't work. It can't work.

That calculation was about how long it would take to split the CO2 atmosphere only looking at the amount of sunlight available and efficiency as limiting factors, assuming an extremely high efficiency of 5%. A more realistic efficiency for plants would be .05% which extends the time to over a million years. That does not consider other limts (and there are many). But even if it worked, it isn't terraforming.

You would end up with a poisonously thick oxygen atmosphere and a layer of carbon. Under those conditions, the carbon would burn spontaneously. Actually, a person would burn nicely under those conditions. Realistically, it would never get that far.

So, unless the atmosphere is dealt with technologically, I agree that flying cities would make the most sense, if people want to live there.

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Getting the materials to build floating cities onto Venus would require mass transportation of materials through space; i.e., in a practical sense, asteroid mining on a large scale. If we can do that, which would require a signifigant longterm human presence in space (or self-replicating machines) then we'd already have plenty of habitats to choose from. Deciding to live on Venus would be a vanity project of sorts. (Not saying it would be bad, just no major motivation to do it. Although vanity can be a pretty major motivation )

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
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"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

The clouds actually reflect away a rather large fraction of the sunlight. If you want to cool Venus, you need a sunshade. If you blocked off all the sunlight, it might be possible to freeze out most of the atmosphere in about 300 years (there may well be factors that extend that time). That might be the first step in terraforming Venus.

The key problems for Venus:

- Far too much atmosphere.

- It's hot.

- It receives too much sunlight (this would be an issue even if it had a reasonably thin atmosphere).

- It rotates very slowly.

- There is very little hydrogen and less water. If it was all converted to water, and if the atmosphere was at a reasonable pressure and temperature, it's unlikely there would be enough for standing water (no oceans, no lakes, nothing) and a useful hydrological cycle. Importation of water (or hydrogen) would be a requirement.

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Add to that that the atmosphere it has now is toxic and corrosive, even at the 1-atmosphere altitude.

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

I like the article. I think we should abandon talk of terraforming venus and focus on colonizing the clouds. Maybe we should call it atmo-forming or aero-forming since the depths to the surface is still terra incognito, or would that be venera incognito.

There may not be a lot of lot of free hydrogen, but the sulphuric acid contains bound hydrogen and oxygen. Free them up and, presto chango, you've got water.

Buckminster Fuller had plans for floating cities and he was only thinking of Earth. I think you needed a sphere at least a mile in diameter and the if warmed up to human comfort levels, it'd be boyant in Earth's atmosphere. We could build a proof of concept on Earth and test failure modes.

How about it?

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

Shouldn't that be 'venera incognita'?

But yeah, let's do it! Let's build flying cities. We'll mock those silly terraformers from high up, while they sit in their biodome on the surface, mwuhaha.

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If God had wanted Venus habitable, he would have made it that way. Instead he wanted Venus as a proof that evolution is wrong with it's retrogade revolution around the earth, and as a testament to how horrible hell will be with its temperature.

In fact I think that Venus is the lake of fire spoken of in revelation, because the atmosphere is as dense as water. It is probably best that we do not send probes to venus, because they may see demons and tormented people.

And where would you suggest we should send probes to find angels and a pearly gate? Uranus?

Sorry, couldn't resist.

Anyway, won't the demons get hurt by the sulphuric acid in the atmosphere?

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This user is currently on a smooth slope of Mount Improbable

No, the demons are immortal spirit beings, it is the people that are being hurt by the sulphuric acid, but God made them where they are physical beings and can feel pain, but cannot die.

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This user is currently on a smooth slope of Mount Improbable

Believer, please note Rule 12 of this forum, which I quote in part below:

Your personal, religious beliefs about the nature of Venus - unless you can support them scientifically - are inappropriate to this forum. Please discontinue making such statements.

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Everything I need to know I learned through Googling.

Venus would likely not sustain a basic two layer zoned atmosphere wherein the upper altitude provided a blanket of breathable oxygen-nitrogen air. A floating city would have to have its own air supply. This would make a floating city (basically a far-flung variant of a gigantic dirigible, though not in the shape of a giant dirigible,) irrelevant. It would be more technologically feasible from an engineering standpoint to then build a gigantic orbiting spacecraft-town but then why have it orbit Venus? Developing technology for a floating city would also be highly problematic. Turbulence in the upper atmosphere of Venus would again make an orbiting spacecraft-community safer, but why bother?

The (strong) domed surface structure is a more interesting idea. But actually, I think a hypothetically transformed Venus might not be absolutely impossible if approached from the standpoint of many combined and simultaneously running technologies. As a simple sketch, just to illustrate:

1. Nanotech and bio-nano-altered CO2 transforming atmospheric implants. (This is not intended to transform Venus, but instead designed as an initial step toward altering the planet from a "Level 1" (present state) to a "Level 2" – still highly toxic but different from previous state.)

2. At the same time, ground implanted systems that receive organic carbon raining toward the hot surface preventing carbon dioxide from being liberated again. (This is the magic part because I have no idea how that could be done.)

3. Simultaneously build very strong domed outposts housing automated systems and later inhabited by people. The structures are designed for research, monitoring and control of the above systems. And simultaneously:

4. The planet is prepared by a very powerful cooling mechanism. This is necessary so that CO2 enters a liquid state. Liquid CO2 must be maintained or aided by some process to remain at a pressure and temperature that tolerates a liquid state all the way to the ground. The construction in solar orbit so that it provides continuous temperature-lowering shade, a series of gigantic interlocking strips of material to block solar heat.

All the coordinated systems are related so as to accommodate emergent modifications, in other words, the phenomenon of the sum of all applied technologies being greater than the individual parts.

5. Massive, planet-wide applications to transform Venus into a dry, warmer Earth-sized world with an unbreathable atmosphere somewhat resembling Mars in its present state.

6. Introduction of water during the above processes. (Don't know how.)

7. Introduction on the surface (which is already inhabited by generations of domed dwellers) hybrid plants and animals to aid gradual transformation toward more Earth-like conditions.

8. Landscape beach resorts and open Venusian Tiki Bars for tourists.

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"Insignificant molehill sometimes more important than conspicuous mountain." - Charlie Chan

The numbers I found suggest there is 90 times more atmospheric pressure at the surface of Venus than there is on Earth. This means you have to get rid of 89 times the weight of 1 Earth atmosphere to reach an Earth-like pressure at the surface. Right? Is that even worth it? Sure there is money in tourism, but I think it's going to be floating luxury liners/hotel/casino/ships that will float through the clouds, while cocktails are served inside. What better backdrop than continous lightning storms outside the (reinforced) window, while sulphuric rainstorms batter the (non-corrosive) hull? Don't try to tame the turbulent goddess Venus, but admire her with awe and respect.

Ok, I think that last bit requires a too

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OMG.He certainly did not mean that seriouisly.DON'T BULLY PEOPLE!

Some extra-solar rogue impactor would be the fastest way, with an off center strike to blow off atmo, spin it up and form a moon. Followed by some giant comets for water. Then launch an occulter disk.

Ah, the Michael Jackson Approach.

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If you were referring to my post (not sure) the last bit was a humorous touch.

You can also enjoy the wild untamed Venus from your pressure dome window as such domes would exist for many years while hypothetical simultaneous processes effected changes.

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"Insignificant molehill sometimes more important than conspicuous mountain." - Charlie Chan

Many Soviet and USA probes were alredy sent, no demons,no tormented people, sorry .Take a look on this pictures: http://upload.wikimedia.org/wikipedi...a14Surface.jpg

http://www.mentallandscape.com/C_CatalogVenus.htm

http://www.mentallandscape.com/V_Venus.htm

It's atmosphere is only 15 percent of water density and, in fact, if you stay on the surface of Venus, unless you land nearby some active volcano, you will see no fire lakes, lighting as frequent as on the Earth (the extreme lighting observed by Venera probes was probably caused by a nearby volcanic eruptions, higher SO2 content in the atmosphere during the 70-80s support this theory, now Venus Express don't observed that extreme lighting, probably that volcano calmed down or became dormant) and Venus's basalt plain looks just like normal barren basalt plains in the volcanic areas of Earth.And yes, there will be dark, but only about as on absolutely overcast day on the Earth.And sulfuric acid rain will not fall, because it will evaporate about 25 km above surface, like virga in the deserts of Earth.The only bad thing about Venus is temperature of 500 degress Celsius, in the highest mountains 370 degress.And pressure is not as bad, just like 1 km deep ocean.And on the highest muntains there are only 44 atmospheres.

I guess this will be regarded as "impossible", but why not send humans to Venus?!Some material can survive 5000 degress Celsius and thousands of atmospheres (like carbon, used, for example, in the Galileo probe), and you are ****ed off by 500 degress and 90 atmospheres!Make spacesuits from light carbon, base from the some heat and pressure resistant metals and carbon, get O2 from CO2, periodically send some probes to upper atmosphere to harvest H2SO4 and then make H2O from it .Of course, hire some good engineers first.After it's building, the base will be perfectly self-sustainable.Materials and metals would be mined by machines.Than sold to Earth and we will have no problems with the depletion of the Earth's resources.Remember, Venera probes survived only 58 minutes not because of the Venus's conditions, but because;
1.It was 70-ties.
2.Probes must be launched from the Earth and so no extra heavy and sturdy metals or other materials can be included.

My base will be perfectly self sustainable, will make great benefit to the people (mining) and will not cause severe problems in non adapted or genengineered humans with gravity (remember, Moon's gravity is only 1/6 that of Earth's, Mars only 1/3, but Venus about the same as Earth's), and will not requrire some at the near future impossible and multigenerational godly projects like Venus's terraforming.
It will require only great engineering, resistant materials, good administrative, periodical repairs (using machines) and orbital or Moon-base (because launching that tons of heavy metal and other junk from the Earth will be absolutely uneconomical), but it will be expandable using robots and materials mined on Venus and actually will provide more comfort and be healthier than for example Moonbase, because of the familiar gravity.
IMHO no terraforming is needed in the next 400 years, because we can build substainable base on non terraformed Venus at little future technological advancement and money.Terraforming will be a gigantic waste of time and money in the next 400 years.Instead, we should more concentrate how to build self-sustainable colonies on the barren and hostile, but mineral rich planets of our solar syatem.We will need them when we will take the next future greatest steps in the human's history-terraforming of the planets of the Solar system, of course, including Venus and interstellar travel...

And I know, you guys are thinking of Venus as of a hell planet, because you have seen Magellan pictures.They are just false orange coloured radar images that show no atmosphere and do provide the detailed map of Venus, but not the real impression of being on the surface of Venus.But Venus is not orange hot fire and brimestone, but new opportunitty for humankind!
It is a very intersting planet, and if we send more probes to it, we will certainly detect thing even more exciting than on the Mars!Open eyes, people.Do Venus deserve neglect and fear only because it is hot?I think geologically active planet is more resource-rich than some geologically dead Mars or Moon.Thought practically, vacations on Venus are not the goal, but the goal is, overcome the coming natural resource crisis that will come in the next 200 years.Yes, there is no oil, but the metals are certainly useful!

"
I know this thread is about terraforming, but would a sheltered dome be a better solution for colonisation? Lets say you bring all the materials from Earth, air-drop them on Venus and have robots (that can withstand the heat and pressure) assemble it on the surface. People can them come down in ships/special shuttles to dock with the base without exposing themselves to the atmosphere.

Would that be possible or am I underestimating the conditions?

Quick question here: I just read that Venus has a pressure of 90 Earth atmospheres. Will ships ever be able to take off after landing on Venus? Does a dense atmosphere means it behaves more like water (providing better lift when gaining altitude, like manouvering in water) or is it going to create so much downward force that your ship is stuck on that planet?
"

Actually, almost all people here are OVERESTIMATING THE CONDITONS!!!
Yes, it will take off without problems, only need a stronger rocket and it will be slower.

And Venus's atmosphere at the ground level is no more toxic that for example Mars's, acid will not survive on the pressure and it is almost pure carbon dioxide.