Venus has a LOT more CO2 than Mars does. And the band that people are envisioning putting the aerosats in has, well, less sulfuric acid than does the denser lower atmosphere.
Honestly, probably the realistic view is that it never makes sense to colonize, or even send long-term human presence to, any planet besides Earth. But to the extent that we want to dream of human presence on another planet, I think that the big obstacle to Venus is not the hostility of the upper atmosphere, it's the difficulty in getting any non-gaseous resources out of it.
At the very least, it seems like sending a robotic balloon probe to Venus to try to tool around in the upper atmosphere for an extended period of time is at least as worthwhile as sending another lander to Mars.
It would be much cheaper to establish a dozen independent biospheres here on Earth than one off Earth. Put one in the Canadian Shield, another under the Australian desert, etc. If scattered well, several should survive even a Chicxulub-class event.
But I suspect you mean something different than independent biospheres. If so, what risks are you thinking of?
> several should survive even a Chicxulub-class event
That's an interesting proposal. I'd love to read a study on that.
> But I suspect you mean something different than independent biospheres. If so, what risks are you thinking of?
Well there are degrees of independence. Perhaps "isolation" in the systems engineering sense is a better term. There are a lot of high-risk probabilities that arise as technology advances - and the Fermi paradox isn't encouraging about our chances. For some example risks, let's say grey goo, cybernetically enforced self-destructive tyranny and unexpected stable artificial black hole. In some case, the light-minutes of separation may make the difference.
It might make more sense to build an artificial orbital habitat at L5 or the like, but these seem so fragile compared to biospheres that could be constructed on Mars. Being out of the gravity well is a huge advantage, but the gravity on Mars is low enough that space elevators become a real possibility. Perhaps Ceres is a good compromise - lots of water, metal rich asteroids all around.
The Chicxulub impact had global consequences, but far enough from the crater would have been survivable in any bomb shelter. http://users.tpg.com.au/users/tps-seti/climate.htm gives an estimate of the damage radius, with 1 psi overpressure to 4000 km. While it says there was a global firestorm, the most recent analysis believes that that wasn't the case, see http://www.exeter.ac.uk/news/featurednews/title_430274_en.ht... . It does says that being on the other side of the planet would have been worse than North America, in terms of heat flash, so the Canadian Shield would be survivable, as would most nuclear bomb shelters in the world.
It's very hard to model those risks. A non-terrestrial habitat will certainly be more fragile than one on Earth, and easier to fall prey to a malicious computer attack by rogue AIs. A gamma ray burster would be more survivable in a shelter 1,400 m underground[1] than anything we are likely to build soon on another planet, or Ceres. A "Dark Star" scenario as in Fritz Leiber's "A Pail of Air" feels more likely than an unexpected stable artificial black, and in that story, access to nuclear fuels, along with a stockpile of liquid atmosphere and frozen materials, helped keep civilization going. Or perhaps the Free Peoples of Ceres will send an asteroid killer our way, to keep the solar system from being infested by flatlanders.
So while there are scenarios where separation is important, there are also scenarios where separation won't help, and might end up taking funding away from something which would have helped. With probabilities that low, and with such high error estimates, it's hard to tell which approach is best. The cheapest is self-sufficient here on Earth. If that works, then there's the base knowledge for how to set that up off-planet.
([1] I refer to the Laboratori Nazionali del Gran Sasso, which is a neutrino lab. While not the deepest lab, it's one with an access road instead of an elevator. Very handy if you want to supply your colony.)
Most people who have ever tried living in an isolated biosphere on earth decided, after some number of months, that cities and trees and sky were pretty desirable, opened the airlock and left. Possibly it would work on another planet with no return vehicle.
In any case, the first step would be to develop a long-term, viable independent biosphere. We haven't yet figured out that one. Once we get that working, we need enough excess free capacity to raise and educate children to be the next generation of biosphere caretakers.
Economy is an engine of progress, but some people raise it to the level of a God. It's a tool, not a justification. We shouldn't limit our actions only to those that turn profit, 'lest we turn into mindless drones generating entropy without much purpose.
>Honestly, probably the realistic view is that it never makes sense to colonize, or even send long-term human presence to, any planet besides Earth.
I think it could make sense when we have robots that are able to mine material and construct habitats without requiring human supervision. Just build the robots, drop them off on Venus, Mars, etc, then come back in 30 years and sell condos.
> I think that the big obstacle to Venus is not the hostility of the upper atmosphere, it's the difficulty in getting any non-gaseous resources out of it.
We can get non-gaseous resources out of Venus accessible asteroids. Venus could supply two things -- a beautiful and relatively friendly place to live and also fluorine condensed out of its atmosphere.
I could envision huge aerostat supported structures hundreds of kilometers long that house electromagnetic accelerators to launch raw materials into orbit. Rotating tethers could deposit cargo carriers into the Venusian atmosphere at hypersonic speeds, to deploy ballutes and slow down through aerobraking and then to float awaiting retrieval. In doing so, the tethers would re-accelerate themselves to haul other cargo up from hypersonic aircraft.
Maybe it's not economically and politically feasible now or ever, but it's tons of fun to think about. This sort of thing also demonstrates that it's not physically impossible.
> At the very least, it seems like sending a robotic balloon probe to Venus to try to tool around in the upper atmosphere for an extended period of time is at least as worthwhile as sending another lander to Mars.
Exactly. Enough with Mars already. Red sky, red sand and red rocks : it gets old, frankly.
"Honestly, probably the realistic view is that it never makes sense to colonize, or even send long-term human presence to, any planet besides Earth."
The sole point is the experience of colonizing other planet. We're not looking to get there for the resources (stop for a second and just think out of the box), we're looking to get there to be able to live there as a species.
Honestly, probably the realistic view is that it never makes sense to colonize, or even send long-term human presence to, any planet besides Earth. But to the extent that we want to dream of human presence on another planet, I think that the big obstacle to Venus is not the hostility of the upper atmosphere, it's the difficulty in getting any non-gaseous resources out of it.
At the very least, it seems like sending a robotic balloon probe to Venus to try to tool around in the upper atmosphere for an extended period of time is at least as worthwhile as sending another lander to Mars.