Colonizing Venus may sound implausible or even crazy, but a serious case has been made for it being the best choice that we have
Have you ever imagined living in a city in the clouds? Moving to Jupiter or Saturn would be one way to accomplish that, to build something like Cloud City from Star Wars: The Empire Strikes Back. However, according to scientists and science fiction writers, we could do so much closer to home, in the clouds of Earth's 'sister' planet, Venus.
Although the imaginations of science fiction writers once filled in a lush tropical jungle paradise under the cloudy layers of Venus, the surface of that planet is about as close to hell for us as you can get - temperatures hot enough to melt lead and crushing atmospheric pressures that are the equivalent of being nearly 1 kilometre below the surface of the ocean. So, it may seem a lost cause for human exploration and colonization, and simply an object lesson for the runaway greenhouse effect, but apparently, we shouldn't dismiss Venus so easily.
Most of our attention is currently focused on the Moon, and especially Mars, so lets look at those potential colonies first.
The Moon is especially close by, making supply and personnel runs fairly easy to set into a routine, return trips wouldn't be a problem (we've done it before), and it supposedly has water trapped in its surface that could be of use to us. However, it has its disadvantages as well. While it does have an atmosphere, it's tenuous at best, provide no protection at all against harsh radiation from the Sun and space. Also, the Moon has wild temperature swings, from over 100 C during the day to below -117 C at night. The gravity there - roughly one-sixth of Earth's - would cause health problems too, similar to what the astronauts on the International Space Station have to endure now (causing changes in their physiology, muscle strength and bone density, just to name a few).
On Mars, things get a little bit better, since it has a thicker atmosphere and higher gravity than the Moon, but still less than what we have here on Earth - just over half a per cent of the atmosphere and a little over one-third the gravity. NASA's Curiosity rover has already shown us that's enough air to protect us from the worst radiation from the Sun and space, and it - along with Opportunity - have discovered that there may be ample water sources locked away in the ground. However, the air pressure would still cause problems with habitats and the low gravity would still take its toll on the colonists' bodies. Add in the distance to get there, especially with the limited number of 'windows' we have to get spacecraft into Mars orbit (without having to burn too much fuel) and it becomes a slightly less attractive destination.
Venus, on the other hand, has a lot going for it - at least by comparison. Sure, the combination of 460 C temperature and air pressure nearly 100 times what we have here on Earth would make short work of any colony that we plunked down on the surface. However, there's no need to live on the surface, in fact, we'd be better off just sticking with our heads in the clouds - literally. According to NASA researcher (and science fiction writer) Geoffrey Landis - in a proposal he wrote a few years ago - we could put floating colonies 50 kilometres up in Venus' atmosphere. At that height, the colony would be high up enough in the clouds that it would have access to ample solar power, the air pressure around the colony would be the same as it is here on Earth, so we wouldn't need a pressurized habitat (thus no danger of catastrophic decompression or of Venus' atmosphere rushing in case of a breach) and the atmosphere would protect us from solar and cosmic radiation. Also, at that height, the air inside the habitat would pull double-duty, allowing the crew to breathe while keeping the habitat aloft at the same time. This is because breathable air - the nitrogen, oxygen and trace gases at the right mixture and pressure for us - is actually a lifting gas on Venus, with about half the lifting power that helium has here on Earth. (The example habitat shown to the right is of a small research outpost held aloft by a torus of hydrogen.) Another added bonus is that gravity on Venus is roughly 90 per cent of Earth's gravity, and that would only drop by less than half a percent at 50 kilometres above the surface. So, it would mean far fewer medical problems for long-term residents of the colony. The biggest problems would be supplying our own water and oxygen, dealing with any space weather (since the planet doesn't have a magnetic field like Earth's) and protecting ourselves against sulfuric acid in the clouds.
Landis even points out another benefit as well. If you wanted to send a spacecraft from Venus to the asteroid belt (for minerals and even water), it would take less time and fuel than it would if you launched from Earth. That may be counter-intuitive, since Venus is further away from the asteroid belt, but the planet travels in a tighter circle around the Sun, so it would lend that tighter trajectory to anything launched from there as well (see Landis' proposal for illustration).
Plenty of thought has been put into the concept of colonizing Venus, going well beyond just the simple plans for where we should live on the planet. Check out the Selenium Boondocks blog, where they discuss topics ranging from the essentials, like how to extract breathable air, along with water and other resources directly from Venus' thick, hellish atmosphere, to how to cook your dinner by hanging it outside in the sulphuric acid clouds.
(H/T to Citylab)