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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 *

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)

pavel_lishin 11y ago
Mars doesn't have a magnetic field, either.
- wlesieutre 11y ago
  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 https://en.wikipedia.org/wiki/Inverse-square_law)
3pt14159 11y ago
* 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.
- structural 11y ago
  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.
  - shostack 11y ago
    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.
    - cstross 11y ago
      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.
      - shostack 11y ago
ChuckMcM 11y ago
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.

pavel_lishin 11y ago

Mars doesn't have a magnetic field, either.

wlesieutre 11y ago
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 https://en.wikipedia.org/wiki/Inverse-square_law)

3pt14159 11y ago

* 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.

structural 11y ago
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.
- shostack 11y ago
  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.
  - cstross 11y ago
    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.
    - shostack 11y ago

ChuckMcM 11y ago

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.