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Comment by blisterpeanuts | Hacker News Reader

I'd like to see Venus go towards an Ice Age, which might bring down the surface temperatures from average 462 degrees Celsius to Earth norms, and then maybe the place could be relatively habitable, albeit still with 96% CO2 and clouds of sulphuric acid to deal with.

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The atmosphere of Venus, for what it is worth, is one of the most Earth-like places in the solar system. Breathable air is a lifting gas in the thick Venerian atmosphere, making floating habitats viable. Furthermore, at the altitude where the pressure is 1 atm and a habitat would stabilize (around 50km), ambient temperature is also in the range for liquid water. And even at this height, there would still be enough atmosphere left to provide protection from cosmic radiation.

https://en.wikipedia.org/wiki/Colonization_of_Venus#Aerostat...

The atmosphere also contains high levels of sulfuric acid which would be a bit of a concern. It's definitely a route worth exploring. It just comes with it's own set of crazy concerns.

Iirc, most of the H2SO4 haze falls below the habitable altitude, however there are clouds of it at that height. Biggest challenge would be the lack of water. You'd have to extract hydrogen from the acid to make water.

Yup. Problem with Venus is just that the ground is too far down.

The insane air-pressure ruins it. Basically, the solution to terraforming Venus is to convert the CO2 into water. The problem is that this requires hydrogen that's not readily available to do it. A lot of it.

How much?

At 1 Earth atmosphere, imagine a balloon filled with Hydrogen the size of the planet Mars. It would take two of those.

But then you could scrape enough CO2 out of the atmosphere to make oceans and Earth pressure.

A few years ago I read a paper that suggested freezing the CO2 out of the atmosphere, covering it with a layer of thermally-insulating material, and then putting oceans of liquid water on top of it to keep it sequestered. [0]

[0] - http://www.orionsarm.com/fm_store/TerraformingVenusQuickly.p...

Is that a good long-term solution? Can the CO2 just be left there forever?

The long term solution (per the paper) is to harvest the CO2. The paper states the CO2 will melt over time, but not as quickly as it can be harvested, and that water may even be poured in to melt it faster.

But who on Earth is so fond of CO2? right, plants via photosyntesis.

So why not sending green algae on Venus to harvest that CO2? When the temp drops, send something else, like trees.

Quite SF, but would worth a calculation.

If you want plants to do it, you need water, and there isn't any. The solar wind blew it all away.

Not just because "plants need water", because the chemistry is CO2 + H20 => O2 + carbohydrate

Indeed, you are right. Interesing link on this subject [1], it explains a bit more in detail the greenhouse runway process.

[1] http://www.vanderbilt.edu/AnS/physics/astrocourses/AST101/re...

Plants can't photosynthesize without water. No hydrogen, no water, no photosynthesis to take CO2 out of the atmosphere.

I would have thought you'd do it by making limestone. You just need lots of calcium for that.

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