I think Venus may be the easiest planet in our system to terraform.
I know some of you are Mars fans, but bear with me for a minute. Here are a few facts on Venus:
Venus is close to Earth in size and gravity.
It has water, which is essential for life.
The heat is largely from vulcanism and a huge greenhouse effect.
This greenhouse effect is from a thick CO2 and sulfuric acid blanket.
If this atmosphere thinned out, it would reduce the greenhouse effect.So what would happen if you could cool the atmosphere down for a few decades? And is that possible?
You could perhaps do this with fine carbon powder between it and the sun, but a simpler answer presents itself: Bombard the surface with large asteroids. These would impact, throwing tons of dirt high into the atmosphere, causing a years-long cooling effect for each asteroid, causing a sort of “nuclear winter” for several years for each asteroid.
Logic and science tells me this would cool the planet by blocking sunlight, and this would increase rainfall - a lot. If this was a large enough cooling effect, for long enough, it should thin out the atmosphere. This thinning and cooling would reduce the greenhouse effect and evaporation rate.
Also, Carbon dioxide (CO2) will mix with water in the air to form carbonic acid and dissolved CO2 gas. Both sulfuric and carbonic acid will rain down, and react with many surface minerals to form solid salt compounds. So when that very acidic rain hits the surface, it should chemically react and form salts and release water, but bind some of the acid, as a chemical salt.
The rain will form pools that contain sulfuric acid, carbonic acid, and dissolved CO2 gas. The colder things get, the more CO2 will turn into carbonic acid. [2] Depending on temperatures and mineral content of the surface, more or less of this mixture will form stable salts, resulting in a salty sea, from which water will evaporate back into the atmosphere. This water will have less CO2 and sulfuric acid than before. It will be ‘thinner’ and less supportive of a greenhouse effect.
Venus is known to be volcanic, so new minerals are constantly exposed to chemical weathering [3]. According to Wikipedia, “there is considerable evidence the planet's atmosphere causes the chemical weathering of rock”, so there is some evidence for these ideas.
More research is needed:
Before attempting this, we would need to be more certain of the mineral content of the surface, and it’s susceptibility to acid chemical reactions.
The atmosphere is thick, so larger asteroids would be needed to have any effect.
Some calculations could be done to determine the size, the optimal number, and timing of the asteroids to be used.
Even though NASA's DART project worked, so we have Proof of Concept that we can move asteroides, but more work is needed on moving asteroids.[5]So let me summarize. I think we have the science to do this now. We could begin terraforming Venus simply by dropping a series of large asteroids on it, a few years apart, over some decades of time.
There are some unknowns. Although we have Proof of Concept that we can change asteroids orbits [5] we don’t have any working asteroid tugs, and although maps of near-Earth asteroids exist, we would need that for Venus as well to make this feasible.
It’s certainly a prettier planet than Mars. But I wonder why we don’t just fix this planet instead of trying to get off of it. It’s so pretty here