Suggestion: Waaaaaay up the tech tree, a black hole-related installation that works as a sort of extremely crude terraformer. It's like an ordinary terraforming installation except:
1. It only removes atmo. It can't add any.
2. It operates at about 100x the speed of an ordinary terraformer.
3. It targets all available gases, in proportion to their part of the whole. (If the atmosphere started out as 100 atmospheres of CO2 and 0.1 atmospheres of Methane, this thing would reduce it to 10 atmospheres of CO2 and 0.01 atmospheres of Methane along the way toward 0 of both.)
Call it the "Venus 3000" maybe.
+1 Vote! Nice suggestion!
Actually, I had long considered that a wormhole used to siphon off excess gasses would be a wonderfully efficient way to terraform worlds.
Your idea is to eliminate excess gasses. But I was thinking that a tiny wormhole may allow the transfer of gasses from
a hot world with a thick atmosphere, like
Venus, to a cold world with little of if any atmosphere, like
Mars. The atmospheric pressure should push it through to escape to the low-pressure world.
You'd be terraforming two worlds at once, limited by your tech level, the aperture of the worm hole(s), and the energy required. Though, perhaps there would be risks or downsides? Maybe the radiation may do something to your population? Lower population growth and happiness? Or maybe there's a chance it would explode or something?
Regardless, I think the game really needs better method(s) to terraform with a higher tech level. Currently, it seems too slow.
Why can't we crash icy comets into a planet for liquids and/or gasses? The obstacle would be tugging or pushing the comets into an orbit that impacts a world. Of course, there could be downsides, particularly if the planet is inhabited. And for the short term, it may generate dust which cools the planet for a few years.
I've found articles such as "Icy comets serve as storks for life on Earth." They typically contain water, ammonia, methanol and carbon dioxide, among other ingredients. And the impact may have yielded the energy to drive prebiotic chemistry.
There are other possibilities, too. I found an article about encasing a small planet or a moon in a shell, such as steel and Kevlar fiber. (See "Shell-Worlds: How Humanity Could Terraform Small Planets" on Space.com.) It would allow us to pressurize an atmosphere and make it Earth-like
. Access to space would be through air-locks. And one could build spaceports and industries on the outside that takes advantage of the vacuum of space. That said, it'd be terribly vulnerable to an enemy attack...
I'm also reminded of options in Master of Orion II. Aside from
the usual terraforming, players could build a Planetary Radiation Shield, which changes a "Radiated" planet to "Barren". (Also reduces bombardment damage by 5.) High up the tech tree, players could use Artificial Planet tech to compress/convert an asteroid field into a planet.
Hmm... Maybe, eventually, shield tech could allow one to build a shield around a planet just strong enough to hold or reinforcing a weak atmosphere? Or maybe they could help protect the fragile artificial shell and atmosphere of a Shell-World?