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Comment by 3pt14159 | Hacker News Reader

I know most people are excited about humans on Mars, but I'm far more excited about Venus. 40 or 50kms up Venus is actually quite habitable. Similar gravity, pressure, calm wind speeds. We could build floating cities and create oxygen with floating bioengineered plants that slowly change the oxygen content of the planet. We could use particles or strategically placed solar panel arrays to shield off excess sunlight while we slowly change the atmosphere from CO2 to O2 + other gases.

Mars is just a cold crappy desert.

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Problems with Venus:

* Acid atmosphere and extreme winds

* No easy surface access -> No on-site resource extraction

* No magnetic field -> more radiation

* Larger delta-V requirement for a round trip

* We have no launch systems built for a launch while suspendend in the atmosphere

* Low water content

* Much less signs that suggest previous habitability (hence Mars is more interesting)

Mars doesn't have a magnetic field, either.

True, but it's further from the sun. The amount of stuff hitting you decreases with the square of distance, and Mars' closest distance from the sun is roughly twice Venus'. Assuming the simple "sun as a point source in a vacuum" model holds, Mars gets less than 1/4 the radiation of Venus.

(https://en.wikipedia.org/wiki/Inverse-square_law)

* Acid atmosphere is mostly near below the surface, and is fixable in the long run.

* Suface access can be done by robots, resource extraction can happen on the surface and balloons can lift the resources to the habitable zone.

* No magnetic field, agreed. Problem.

* Larger delta-V, less of an issue in the long run. It's easier to get to Detroit than Cuba from Toronto, but most people winter in Havana.

* Launch systems are easier that bioengineering.

* Water can be imported or synthesized. We'll have lots of extra O2 with all that CO2 we'll be converting.

* We haven't really looked at Venus. We've sent some soviet probes in for a couple of hours each back in the 80s, and they focused on the hellish surface.

In terms of long term development of human cities, I still think Venus is a far better candidate than Mars, even if Mars is easier for now.

We still don't have a set of robots whose lifetime will be measured in days, not hours. Really, if the atmosphere was fixed a bit then most of what you said would become possible, but it's unclear just how that's going to happen, especially at first.

What sorts of implications might there be if we actually had a way of fixing the atmosphere? I imagine that it is intimately connected to other aspects of the planet.

One huge problem with Venus, even if we could "fix" the atmosphere, is that there's no working plate tectonic system. It's hypothesized that the build-up of stresses actually leads to the crust liquefying every couple of hundred million years. There's also the slight problem of the Venusian "day" being 116.75 Earth days (compared to a year 243.69 days long). It's not tidally locked but there are some pretty fierce winds in the stratosphere (at ground level the atmosphere is so dense -- 92 bar pressure -- that wind speeds are on the order of 1 m/s).

Next, there's a huge amount of heat trapped in the atmosphere. "Fixing" it isn't just a matter of dumping comets full of water into the atmosphere, there's the slight matter of Venus being a whole lot closer to the sun that Earth, and receiving a much higher level of insolation.

All in all, the lack of a magnetic field is relatively minor compared to the other issues.

Flip side: Earth atmospheric gas mix at STP is actually a pretty efficient airship lifting gas on Venus and would provide about equivalent lift per unit volume 30-40km up in the stratosphere as hydrogen provides to a terrestrial airship at sea level. (In other words, you could in principle build a zeppelin where you could walk around inside the lift cells of in shirt sleeve conditions.) And there's still a chunk of atmosphere above that to provide radiation shielding. So a human "base" in the Venusian cloud tops is conceivable, albeit technically challenging.

Thanks for all the details!

Given your knowledge of the science fiction space, are you able to recommend any books that delve into what living/working in a Venusian cloud-top base might be like at the scientific level of Seveneves, or similar to the "slice of life" approach of PlanetES? I always had a thing for wanting to know more about the nitty gritty of living in such a "Cloud City" type of place.

Coming at this a little sideways, the Eclipse Phase sourcebooks might be what you're after - Sunward ( http://eclipsephase.com/releases/sunward-inner-system ; it's liberally licensed so there are legitimate torrents around as well ) is likely to have the most about the Venus aerostat habitats in-setting. Eclipse Phase is intended as an RPG but it's extremely hard sci-fi that at times feels it's as much a futurological thesis as a game.

One of the solutions proposed since 1960s is to engineer a kind of atmosphere-floating algae that would synthesize just the right amount of H₂ to keep themselves afloat in the habitable belt of the atmosphere. Without predators and with plenty of CO₂ and access to NH₄ and such, they would multiply quickly and deplete the excess CO₂ from the atmosphere in a century or two.

However it still has an atmosphere, Mars, not so much.

So if you take it from the perspective "the atmosphere is fixed", and you pick either Mars or Venus, then Venus seems to be a better choice.

Both Mars and Venus would need some sort of radiation shield.

Selenian Boondocks had a great series of posts on living on Venus a while ago. The short of it is that there's lots of useful stuff in the Venusian atmosphere, and it's much easier to harvest things from the medium you're floating in than to mine it. I'm not going to speculate on terraforming since that takes so long but there's plenty of reason to go to Venus.

http://selenianboondocks.com/category/venus/

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