IANAS but I think there are some problems with trying to use the hydrogen. AFAIK the only way to use hydrogen as fuel is to burn it or feed it to a fuel cell. Both methods boil down to the same thing: combine the hydrogen with oxygen, producing water and energy. So you end up recombining the hydrogen with the oxygen you just liberated and recreating the water you just split. Your only useful end product is energy and you could have taken that directly, and more efficiently, from the sun farm. If you want to use the hydrogen for storing and transporting the solar generated energy that’s fine but you can’t burn it all and still have oxygen left for terraforming.
Okay, previous threads on terraforming Venus can be found here and here. Suffice it to say that it ain’t gonna be easy. Previous threads on terraforming Mars can be found here and here.
dalovindj, don’t hate what we are. All life feeds on life. Were we to genetically engineer ourselves so that we could survive on sunlight and oxygen alone, we’d still be wiping out life. People would claim that we’re depriving other animals of oxygen and we’d be blocking plants from getting sunlight. Not to mention our immune systems will kill billions of nasty organisms all the time without our ever noticing it. Our houses crowd out plants and animals, and no matter what we do, we’ll kill something. It’s entirely possible that there’s some form of life out there which will eventually wipe humanity out in order to preserve it’s own existance (I personally intend to go down fighting, it may be the law of the jungle that only the strong survive, but I’m gonna make the bastards suffer before I go.).
Well, I wasn’t talking about using the hydrogen immediately in fuel cells. One thing that it could be used for was rocket fuel. Here’s a thread which talks about using single H in a nuclear powered rocket. In theory, we could reprocess the hydrogen generated by the sun farms into single-H for use in nuclear powered rockets. Additionally, any modern civilization’s going to need hydrocarbons of some sort (lubricating oils, plastics, etc.) so we could use the hydrogen for producing them, since they might not be naturally occuring on Mars.
One of the beauties about terraforming Mars, is that any industrial operations on Mars won’t have to worry too much about causing air pollution. Any greenhouse gases they can dump into the air will be encouraged unlike here on Earth. Can you imagine it? One day, car makers on Mars will be given subsidies to produce cars that spew out more pollution than they do here on Earth!!! 
No no, “Got any native-americans we can kill?”
Its politically correct genocide. 
Just watch out for Valentine Michael Smith’s nestmates. They might do to Earth what they already did to the planet between Mars and Jupiter.
Come get some!!!
While terraforming both Mars and Venus is well beyond anything we have the resources to do today, terraforming Venus would be orders of magnitude more difficult.
Regarding terraforming Venus:
Venus is almost 500 degrees C at the surface. If you shut off the Sun tomorrow (say, by blocking it out with a big sail or something), it would take a thousand years (or maybe much more) for the planet to cool down to the point where it was even remotely hospitable. The lowest estimate I’ve seen involves blacking out the entire sun, and then waiting at least 650 years if the crust isolates itself from the extremely hot and thick mantle. If it’s a better heat conductor, it’ll take a lot longer than that.
Then there’s the atmosphere, which is 92 times as dense as the Earth’s. I’ve heard radical ideas like using an asteroid to blow through the atmosphere repeatedly, knocking some of it away each time until the atmospheric pressure was low enough. Other options would be to cool Venus to the point where the CO2 freezes, then to collect it and sequester it somehow. But cooling Venus to that point would take additional hundreds to thousands of years.
Then there’s the water problem. Water is just as important as an atmosphere, and it looks like Venus’s is bound up inside the crust in the form of hydrated minerals. You’ll need a nanotech super-technology to free all that up.
But if you’re going to presuppose the virtual ability to remake planets using nanotech, is Venus even the right candidate? Wouldn’t it be better to terraform the Moon? Hell, we’re moving asteroids and comets around at our will, blowing atmospheres off of planets, freezing them, etc. Surely we can figure out a way to terraform the Moon. It’s too small to hold an atmosphere, so we’ll have to figure something out. But the coolness factor would be off scale. Can you imagine being able to look up and see another, smaller Earth? Can you imagine sharing TV networks with them like Americans do with Brits?
It’d be just awesome. Maybe we should just go and grab Mars and drag it nearby.
Or here’s a way to solve both problems - use tiny nanotech replicating machines to bind up CO2 and power themselves out of the atmosphere, then ride the solar wind to Mars, or power themselves there with fuel manufactured on Venus. The machines themselves could be made up of carbon and oxygen structures that could be disassembled at Mars and turned into more CO2. Let these things replicate on Venus by the trillions, and fly themselves to Mars, taking all of the excess Venusian atmosphere. The exact amount needed to make an atmosphere on Mars flies to Mars, and the rest navigates itself off into space permanently.
Another fleet of these things might carry other excess compounds off of Venus and either send them to the Moon, Mars, or Earth as needed. The rest could be shed.
And then when we’re done with that, we can start talking about how much fun we could have with the Jovian moons. Might have to move them away from Jupiter and it’s damned radiation, but we’ll figure that out.
Then one day, we can hollow out Pluto and make a mondo city out of it, hitch Neptune up to the back for fuel, build a big mother of a rocket engine out of some useless moon or something, and take a multi-generational galactic cruise for a better interstellar neighborhood. 'Cause now we want to roll up our sleeves and REALLY start thinking big. (-:
Wait a few hundred years, and you’ll have a more massive Mars, a slightly smaller Venus with a 14psi atmosphere,
And of course, that sail you’re using to block the Sun is going to have a lot of pressure on it, and will have to be kept in place somehow.
Oops. Strange editing error.
Kudos, Sam! 
You absolutely shot down Venus (my throwaway suggestion) pretty convincingly.
You left open the possibility of “fun with the Jovian Moons” where I reckon the best chances of life already exist and where perhaps humans might be able to set up something of an outpost. (**Beagle might find Europa too expensive - maybe Ganymede?). We’re gonna have to deal with radiation no matter what.
Sam, I know an easy, and fairly practical way of preventing a Lunar atmosphere from escaping: A giant geodesic dome covering the entire surface! (Of course, there’s the problem that one side of the Moon tends to face the sun for long periods of time. Have to make sure the atmosphere circulated well enough that one side didn’t bake, and the other didn’t freeze.)
**Beagle - **
The more recent reports are very hyped. A NASA spokesman was talking about how you could simply drink the stuff straight out frmo the ground.
Most likely, the majority of underground water on Mars is trapped in hydrous ferric salts, and that means a lot of messing about to remove the water.
I, Brian: you might be right. My main contention is that, dammit, if there is one thing we can do - it’s generate some carbon dioxide. For one thing, if we go, we’ll exhale it. As for water, if the poles are mostly water ice, shouldn’t that be enough? Just getting some people there for an extended stay would be one of the greatest accomplishments in human history.
I like to let the more scientific minded pick through the details. But, some things just don’t make sense on their face. To me, the notion that a lack of carbon dioxide ice in the northern cap precludes any attempt to generate an atmosphere on Mars sounds silly. If we are talking centuries / millenia - I think we are -can’t let a little ice setback stand in the way. The whole no-molten-core thing is bad, I understand. Radiation problems abound?
Corbomite: what kind of radiation? What about being close to Jupiter, other problems arise, right?
Since we’re talking about engineering on a planetary scale, let’s just melt Mars’s core again. Put a big magnetic field around it, and let its rotation induce eddy currents in the core and melt it. No problem!
And while we’re at it, let’s move Mars a little closer to help it warm up. I think a stable orbit somewhere around 1.1AU should be nice. Just gotta make sure there is no interaction between it and Earth.
And let’s move Venus back to maybe .9 AU, move some of its atmosphere to Mars, and shed the excess. It’ll take a thousand years to cool down, but nanotech has made us all immortal, and we tend to think in the long run these days…
As for the moon, we’ll we’ll just have to get it spinning again.
Beagle - Nasty radiation, with teeth!
Hopefully Sam can say more, yet I assume he was referring to Jupiter being the only body in the Solar System that actually net releases more energy (radiation) than it absorbs. Mass-wise, Jupiter is better than 4/5’s of the way towards being a star.
Hey, with proper muzzle shielding, that can be mitigated. Besides, the mutants, clones, robots, and androids will not care about a little radiation. You would not be bluffing, or Maneuvering would you Corbomite?
Sam, I like the push-the-planets around idea. How? Planets are pretty big.
JUpiter has a huge magnetosphere, millions of times more powerful than the Van Allen belt around the earth. Charged particles are accelerated in the belts and bathe the inner moons in extremely intense radiation. The charges are so strong that Io gives off bursts of radio waves because the difference in charge on one side of the moon from the other causes a huge electric potential buildup of charged particles.
I’m not sure if all the moons receive enough radiation for it to be fatal if you stayed for a long time. Certainly the inner moons like Io would be bathed in enough radiation to fry you. I’m not sure about Ganymede and Callisto, but I suspect they also get too much.
BTW, this is based on new data from Cassini, which flew past Jupiter last year and found that the radiation belts were MUCH bigger than had previously been thought.
Cassini, named after the Italian-French astronomer Gian Domenico Cassini, patron saint of backyard astronomers, who upgraded his Toys 'R Us telescope to a Dutch-type and resolved Saturn’s Ring into Rings (the space between aptly named the Cassini Division)
Atmosphere, low-to-no radiation, outside of Saturn’s magnetosphere. oceans of ethane
(more on the Cassini-Huygens mission from JPL and NASA)
Beagle: How to move the planets? Well, we’re talking about massive engineering projects using nanotechnology - freezing Venus, blocking the sun, slamming asteroids through the atmosphere, etc. If we can do that, we can figure out how to move the things. Build a space elevator (a BIG one), and start moving mass up and flinging it off the end. Make the elevator really, really long so that the mass at the end is going at a really good clip. Each time you do that you’ll slow the planet down a bit.
Or maybe we can use some kind of jiggery with Jupiter and its magnetic fields to fling a moon out of Jupiter’s orbit and crash it into Mars at just the right angle. That would also help heat it up, and increase its mass.
The point is, if you’re thinking big enough to engineer at planetary scales, it’s not much of a stretch to start talking about re-engineering the entire solar system. How about if we just dismantle the more useless planets and use them to build huge solar collectors to power our extremely powerful civilization? Eventually, you can build a Dyson sphere completely around the sun, and make sure those weasels at Alpha Centauri don’t get a single erg of your energy.
NASA has actually figured this out. No shit. I don’t remember the details, but here’s the gist of it:
In X number of million (billion?) years, the sun’s going to be getting too hot for comfort on the Earth, so you hurl a large asteroid close to the Earth, and it shifts the Earth in it’s orbit enough that things are comfy. You’ll have to do it again in another 6,000 years (and every 6,000 years thereafter) to keep things on track, but it’ll work. I have no idea how big the asteroid’s supposed to be, but obviously it can’t be very small.