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Comment by rootbear | Hacker News Reader

Nice summary, thanks. If Mars never had time for life to develop, that would be a sad thing. We could have had neighbors. In some ways, Venus is even more sad. It's much closer in size to Earth with much higher gravity than Mars, which I think would be better for human colonists. But Venus is a mess, so that's that.

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The deal with Venus: dat atmosphere. She's a true sister to Earth in mass, gravity, and composition. She's also good evidence that Earth had a vastly thicker atmosphere at one point. Right now Venus has 90x more atmosphere than we do. And look at the proportions:

    Major:       96.5% Carbon Dioxide (CO2), 3.5% Nitrogen (N2) 
    Minor (ppm): Sulfur Dioxide (SO2) - 150; Argon (Ar) - 70; Water (H2O) - 20;
                 Carbon Monoxide (CO) - 17; Helium (He) - 12; Neon (Ne) - 7

That's interesting because if you take away the products of volcanism (a major source of sulfur dioxide and carbon dioxide here on Earth), you're left with... Nitrogen... Argon... Water... and noble gasses. Look familiar?

The best thinking right now is that Earth outgassed and held on to a similar volume of gasses as Venus. But since we had a substantial volume of liquid water on the surface, the oceans naturally absorbed CO2 and then deposited it on the sea bottom as carbonate minerals. (Life eventually learned that trick too, leading to things like shells)

So limestone, dolostone, chalks, calcite, marble, etc.... all those carbonates are likely the product of our liquid water oceans drawing out the vast bulk of the C02 in our atmosphere, leaving relict gasses in its place. Same starting point but we ended up with vastly lower pressure and vastly different final composition.

Venus had no such luck. She suffocates forever.

http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.htm...

The water, while scarce as part of the whole atmosphere, is concentrated within the sulphuric acid clouds (25% by volume). So if you can float a balloon with a pump at that altitude, you should be able to get water fast enough. Human or robotic explorers should be very safe in the cloud deck, with low ambient pressure and temperature. You may even be able to dissociate the hydrogen from the acid itself.

Wait, so are you saying if we can suck CO2 out of the atmosphere on Venus, it would be livable eventually?

That math and engineering is wildly beyond me! But one suckypoo downer once you do sequester all that CO2? No planetary magnetic field.

In short, scientists think there has to be a convecting, rotating, liquid metal core in order to create a substantial magnetosphere. Venus's planetary core is almost certainly missing one, two, or three of those things.

The fact that Venus is extremely hot on the surface (460ºC) is at least partially assisting with creating a "stagnant lid" tectonic regime where no heat-venting plate action is seen. So if the surface of the planet is nearly as hot as the mantle and the mantle is nearly as hot as the core, convection doesn't happen. Wiki "geothermal gradient" for more.

Thus no magnetosphere, thus no electromagnetic deflection of the sun's blast. Not a dealkiller, but certainly not preferable if you'd like to move in someday.

As a kid I would imagine aliens helping us pull Venus into the same orbit as Mars and combining them to form a new planet like ours.

Venus is a great planet to colonize, much better than mars. You just need to be 50km up!

http://spacemonitor.blogspot.com/2007/05/floating-city-on-ve...

The one problem will be that once you're established in the clouds, access to resources down below will still be difficult. You'd be living in a desert. Whereas if you're set up on Mars, all its surface resources become available.

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