Terraforming Venus: Floating Cities and Asteroid Impacts
Could we someday terraform Venus? There are several possible solutions for the (admittedly many) problems associated with living on the unbearably hot planet.
While most talk about terraforming known planets focuses on Mars. And while terraforming Mars would undoubtedly be simpler, Venus is actually surprisingly Earth-like. The main obstacles to terraforming this planet include the oppressive atmospheric pressure (a whopping 91 atmospheres), the temperature is far too high (an average of 864 degrees Fahrenheit), and there is no oxygen in the atmosphere. (Plus, it occasionally rains sulfuric acid, so there's that.) This may make Venus sound like a veritable deathtrap, but luckily enough these issues are all connected to the same problem: too much CO2. Here are four proposed solutions to this issue:
1) Freeze the whole damn planet
Counterintuitively, we may be able to fix the problem of Venus being too hot by making it too cold. If we used some kind of gargantuan solar shade in order to block Venus's sunlight, the atmosphere would cool hundreds of degrees, to the point that the carbon would freeze and literally fall out of the sky, piling up in drifts like a huge snowstorm. The shade would also block solar wind, which would solve the radiation exposure problem. There would be a lot of carbon to somehow dispose of, but the planet may be habitable after this drastic measure.
2) Smash it with asteroids
[Credit: Wallpaper Sam]
This option is exactly what it sounds like. Many scientists have theorized that one could "blast away" Venus's atmosphere by shooting asteroids at it. This is obviously a daunting and impractical task in itself, as each asteroid would likely only eject the atmosphere directly above it, which means it would take many, many asteroids to even begin to eject all of Venus's atmosphere into space. Furthermore, without further intervention, the atmosphere would likely be pulled back into Venus's gravitational field fairly quickly.
3) Infect the planet with genetically engineered bacteria
Carl Sagan proposed in 1961 that we could genetically engineer bacterial life forms to "fix" carbon on Venus and make the air breathable. Unfortunately, this particular solution has been invalidated by the later discovery that Venus has a much denser atmosphere than we originally thought, and as a result it would quickly convert any carbon that was contained in organic molecules back to carbon dioxide. Also, Venus has no magnetic field, and as a result loses most of its naturally occurring hydrogen to space. As bacteria need hydrogen in order to produce organic molecules, they would need a steady supply of hydrogen in order to process carbon dioxide. Sagan later conceded that this solution would not work, but his groundbreaking theory led to a variation that has thus far not been debunked:
4) Floating Cities
[Credit: TriStar Pictures]
The final option is something of a cheat, but is also wildly entertaining: to build Elysium-style floating cities embedded in the upper atmosphere of Venus. They would run on factories that would split the carbon dioxide in the atmosphere into carbon and oxygen. We could build with the carbon using the two-dimensional material graphene, which is essentially one-atom-thick pure carbon. Then the oxygen would provide breathable air, keep the cities afloat, and block the sunlight, which could cool the planet to livable temperatures.
The only problem associated with this scenario involves the length of Venus's day, which is 116 Earth days. Cain proposes that we solve this problem using the same enormous space shade, creating an artificial day/night cycle.