Today I'm going to talk about why Terraforming is not an option. Terraforming, of course, is the process of changing a planet into an earthlike one that can support an ecosystem and human life just like earth can. This is often put forward as the goal of space colonization, most frequently with regard to the planet Mars.
I've adequately explained why terraforming Mars is about as realistic as you finding a real-live Pokemon at your front door, and it giving you a hug, and giving birth to magic pixies. It's not going to happen. It is not realistic. It violates basic laws of physics. Mars is unterraformable.
But is Terraforming itself impossible? I mean, if we had a better candidate to start with than crappy old Mars?
You decide. Let's try a thought experiment:
Take Venus. Now, Venus is as bit a load of crap as Mars, but it has some advantages. It has a deep enough gravity well (.96G) that we really don't need to worry about the physiological effects of low gravity, and we know it can hold a substantial atmosphere because it's already got one hundreds of times denser than our own. Geologically, it's the ONLY planet in the solar system which is in any way similar to our own, with a crust, a mantle, a core, active vulcanism (Probably). Despite being crap it is our closest sibling among the planets we've got to work with.
Now, let's imagine our theoretical Pokemon waves its magic wand, and Venus is moved to the same orbit as earth, 93 million miles away. And let's assume its atmosphere is stripped away and replaced with one just like ours. And as part and parcel of this magic, let's assume scads of water are imported as well. How deep? Well, let's take the highest surveyed point, and the lowest surveyed point, and pick an elevation exactly halfway between them. Scientifically this is called the “Datum,” but let's just call it sea level. This would give us about 60-70% water, and the rest land, not unlike earth. Let's also magically speed up its orbit to a 24 hour day. This gives us a planet as close as it's feasible to get to our own. It's pretty damn close. Thank you, Pikachu, we won't be needing you anymore. Get back to Ash and your other pals.
Now, if we can't terraform this version of Venus, it's a pretty strong argument that terraforming in a nonstarter, right? I mean, really, the planet is 90% done already: water, air. Can we finish the deal without the aid of magic pokemon?
Ok, so let's think it through:
We get a hydrological cycle for free. Water will evaporate and rain or snow or fog or whatever. Actuall, though, we get the BEGINNINGS of a hydrological cycle, because even if we fill up those empty ocean basins, there's no water underground. Yeah, you'll get mud the first time it rains, and some rivers in fairly short order, and lakes, but it will take centuries for water to filter its way underground and form aquifers. How important are aquifers? Very. There is no obvious means to speed this process up.
The planet would be more sterile than the most sterile white room ever produced on earth. Nothing lives on Venus, nothing ever has, nothing could, not with an atmosphere composed of sulphuric acid in vapor form. (Until Pokemonic influence, of course) What this means is that nothing will grow. Period. In order for things to grow we'll need to ship in soil. More to the point, we need biologically active soil with microbes and bacteria and worms and fungi and what have you.
Now, it's a fairly simple matter in enclosed environments to take sterilized soil, mix it with 'normal' soil, and bring it to life, so to speak. This is time consuming, however, and doing it outside of a lab or a factor is hard. You get a drought, you get particularly bad sandstorms, and it's back to square one. What we'd have to do is import thousands of tons off soil from earth, and gradually use it to convert Venusian dirt to soil. That sounds like a lot, and it sounds easy, but it is the merest pinprick of surface area on the planet. You would need to guard it jealously to make sure it doesn't die, your little verdant dot in the sterile wilderness. No one has ever done this, and it would certainly take centuries if it's possible on that scale. And if you want to grow food in the soil, that slows the process down massively.
Now, every river on earth washes silt and salt into the ocean, but the ocean never gets saltier. The process by which this salt is remove from the ocean is unknown, it just happens. My how theory is that it's plowed back under by tectonic subduction. Whatever the process is, what are the odds that it exists on another planet, and works just like here? Pretty much nil. If my subduction theory is correct, then it can't happen on Venus, as Venus has no tectonic plates. The whole planet is one big plate. Hence our ocean will get gradually saltier and saltier over time.
Importing animals will have to happen, but given the limited space they can live on – see the verdant dot above – God only knows how long it would take to set up that aspect of the ecosystem. We have even less idea how long this would take in oceans.
And about those oceans: they'd be shallow. A mile or so in most places, a couple miles in others, but you don't have the super-deep basins you have here. We assume we don't need those as we really only use the top few hundred feet of the ocean, but what if we DO need 'em? What if they fulfil some vital function we're simply unaware of, like, say, cooling the oceans so we don't have a runaway greenhouse effect?
Venus has no moon. That means that animals which rely on the lunar cycle to reproduce – which is pretty much everything that lives in the ocean, to a greater or lesser extent – will go extinct in short order. Some thing will probably be able to adapt, but most won't. It also means no tides. Tides are vitally important because they create the intertidal zone, which is vitally important to life on earth. In fact, it's an increasingly popular theory that life on earth BEGAN in the intertidal zones. So no fiddler crabs or pompanos or clams or what have you.
Terraformed Venus would be a pretty world. Two large continents running roughly east-to-west, and many large archipelagos. One of the continents has a very high elevation, though. Like thousands of feet above sea level. So how much rain would it get? Would it be all green and verdant, or would its elevation make it a shield desert, where most of the moisture in the air is lost before it ever gets there? Is it rainforest, or is it Gobi desert? Probably the latter.
Finally, Venus has no magnetic field. This means it'll be exposed to about 2x as much cosmic radiation and solar wind as earth is.. That in and of itself isn't a huge deal, but every time a charged particle from the sun hits the atmosphere, it flies off into space taking a particle of that atmosphere with it. Over time then – granted, a long time – the lighter elements of the atmosphere will be stripped away, leaving only the heavy ones, resulting in a situation that is at least similar to the way Venus is today.
So is terraforming possible? I mean, we've been given 90% of what we need to make it work, and yet we seem to be unable to finish the deal.