Which planet in this solar system would be most appropriate to terraform?

[onomatomanic]

Also it would seem to me that if the goal is to have large populations in space, that terraforming a large planet would be the worst thing that you would want to do.

Usually, the goal is more along the lines of simply spreading out, though, it seems to me. An extension of the drive that leads all species to try and colonize new habitats when the opportunity arises, as well as wars of conquest and the traditional capitalist "stagnation equals regression" mindset among humans. From that point of view, what matters first and foremost is carrying capacity per unit of effort that has to be extended to create habitable conditions, and planets do pretty well for themselves, in those terms.

I'd say we have the capacity for destruction now. We could if we wanted to bomb most of the Earth's surface with very powerful nuclear weapons and let the destruction, fallout and ash take care of any surviving organisms.

Human life, probably. But even to wipe out "just" all mammalian life, we'd need to devote a lot of industrial effort, for a long time, to building bombs. The impact that, per conventional wisdom, killed the dinosaurs (but, one notes, not the mammals), was the equivalent of millions of hydrogen bombs, says the 'pedia article. And to kill off things like ants and cockroaches, we'd need to try another whole lot harder than that. I wonder if there's actually enough accessible uranium on Earth to use that method...

 

[Ryan_m_b]

Human life, probably. But even to wipe out "just" all mammalian life, we'd need to devote a lot of industrial effort, for a long time, to building bombs. The impact that, per conventional wisdom, killed the dinosaurs (but, one notes, not the mammals), was the equivalent of millions of hydrogen bombs, says the 'pedia article. And to kill off things like ants and cockroaches, we'd need to try another whole lot harder than that. I wonder if there's actually enough accessible uranium on Earth to use that method...

Very true, it would require a disproportionate amount of industrial output to nuclear weapons manufacture. I expect that the biggest cause of extinction would be the knock on effects of the initial blasts, fallout and nuclear winter leading to a domino effect of ecological collapse. Either way the point remains, it would take significantly less effort for us to devastate the biosphere than build one.

 

[onomatomanic]

There's no question that we could cause a mass extinction event if we set our minds to it. When it comes to completely eradicating life on Earth, though, I'm not sure if that would really be a task of smaller magnitude than terraforming another planet. Lots of things (lots in absolute terms, not relative to the status quo) could survive for a long time without much in the way of sunlight. So, even if you discount extremophiles and the like, eradicating life would IMO require permanently altering the atmosphere and poisoning the waters. Which, at least naively, makes it comparable to making a planet which has some sort of atmosphere and water in some form marginally suitable for life, no?

I'm not altogether convinced that this is a pertinent analogy, but while we are obviously more than capable of eradicating species accidentally, we seem to have a surprisingly hard time whenever we try to do it deliberately. It wouldn't surprise me if we manage to resurrect the first extinct species before we ever manage to kill off or even properly control the first unwanted invasive species. Mammoths versus Australian rabbits, say.

In short, life per se appears to be just as resilient as complex ecosystems are fragile, paradoxical as that may sound.

 

[Ryan_m_b]

There's no question that we could cause a mass extinction event if we set our minds to it. When it comes to completely eradicating life on Earth, though, I'm not sure if that would really be a task of smaller magnitude than terraforming another planet. Lots of things (lots in absolute terms, not relative to the status quo) could survive for a long time without much in the way of sunlight. So, even if you discount extremophiles and the like, eradicating life would IMO require permanently altering the atmosphere and poisoning the waters. Which, at least naively, makes it comparable to making a planet which has some sort of atmosphere and water in some form marginally suitable for life, no?

I agree that totally eradicating life is probably not possible, that's why I said devestate rather than eradicate. I still disagree though that destruction is comparable to creation. It's easy and quick to burn a forest down but difficult and slow to reconstruct, especially to the same biodiversity as before.

I'm not altogether convinced that this is a pertinent analogy, but while we are obviously more than capable of eradicating species accidentally, we seem to have a surprisingly hard time whenever we try to do it deliberately. It wouldn't surprise me if we manage to resurrect the first extinct species before we ever manage to kill off or even properly control the first unwanted invasive species. Mammoths versus Australian rabbits, say.

I'm skeptical of extinct animal resurrection for now despite the hype but regardless I make little distinction between accidentally and on purpose. In fact it shouldn't be surprising that when we deliberately try it's harder in the same way that removing a tumour in a limb with a scaple is harder than cutting off the arm with a saw.

In short, life per se appears to be just as resilient as complex ecosystems are fragile, paradoxical as that may sound.

Indeed. This is why It's best not to talk in terms of "life" because it tends to be useless wrt to the conversation. We wouldn't benefit from life on Mars, we would possibly benefit from a stable biosphere formed from ecosystems capable of sustaining a healthy human population.

 

[mfb]

To destroy all life on the surface, I would try to use the solar system:

Build a very good telescope in space to find many kilometer-sized objects in the Kuiper belt.
Build a supercomputer to find a solution for the following scenario: Deflect a small object (probably ~1km diameter) to get a close flyby at a larger object, in such a way that this object performs a close flyby at an even bigger object, and so on. Find some way to add small corrections as the maneuver will not be perfect. Use this chain to kick some ~100km-object out of its orbit, use a flyby at one of the outer planets and let it crash into earth.

There is life deep in the crust, living from radioactive decays (see http://discovermagazine.com/2012/jul-aug/06-tullis-onstott-2-miles-down-microbes-live-radiation for example) - I think you cannot kill this without melting (or removing) the whole crust of earth.

 

[onomatomanic]

I still disagree though that destruction is comparable to creation.

This is obviously true for an individual organism, and obviously true for an ecosystem, if "destruction" means devastation.

However, due to one of life's defining characteristics - its ability to procreate (and procreate at exponential rates at that, under the right conditions) - neither of those obvious truths entails that it is comparatively easy to destroy an ecosystem beyond hope of (some form of) recovery. It's not hard to get rid of most of the weeds in your garden, especially if you don't care what you do to the rest of the plants. But if you then go away and come back after a year or ten... there's going to be weeds there.

Maybe we need a sort of anti-Drake equation parameterizing the likelihood of extinguishing life once life has developed, so we can more soundly compare the two processes?

It's easy and quick to burn a forest down but difficult and slow to reconstruct, especially to the same biodiversity as before.

Ah, I think I see why we disagree. I'd have said that it's even easier to reconstruct a forest than to burn it down: For the latter, you have to start a fire; for the former, you don't have to do anything except wait - life will eventually reconstruct itself.

In fact it shouldn't be surprising that when we deliberately try it's harder in the same way that removing a tumour in a limb with a scaple is harder than cutting off the arm with a saw.

Touche.

 

[Ryan_m_b]

This is obviously true for an individual organism, and obviously true for an ecosystem, if "destruction" means devastation.

However, due to one of life's defining characteristics - its ability to procreate (and procreate at exponential rates at that, under the right conditions) - neither of those obvious truths entails that it is comparatively easy to destroy an ecosystem beyond hope of (some form of) recovery. It's not hard to get rid of most of the weeds in your garden, especially if you don't care what you do to the rest of the plants. But if you then go away and come back after a year or ten... there's going to be weeds there.

Maybe we need a sort of anti-Drake equation parameterizing the likelihood of extinguishing life once life has developed, so we can more soundly compare the two processes?

Ah, I think I see why we disagree. I'd have said that it's even easier to reconstruct a forest than to burn it down: For the latter, you have to start a fire; for the former, you don't have to do anything except wait - life will eventually reconstruct itself.



Touche.

I think we're thinking slightly differently. We agree that even after mass devastation (or even local devastation) biodiversity and biomass will increase as organisms creep back in but what we get back will not be the same as what was destroyed. In fact the greater the devastation the less likely that the re-colonisation of the area will resemble what it previously did.

For a real life example take North Sea cod. Overfishing has devastated cod populations but even if we stopped completely now fishing cod they still may not recover as opportunistic invasive species (jelly fish in this case) have moved in and began to inhabit the former's habitats.

 

[onomatomanic]

I think we're thinking slightly differently.

Right. I actually meant to go back and replace "disagree" with a milder, more appropriate way of putting it in my previous post, but forgot in the end. Anyway, I think we've exhausted this branch of the discussion. :)

 

[twofish-quant]

Interesting. You're right competition and national pride (along with a legitimate worry about loosing out to possible military domination in/via space) had a lot to do with it.

The other interesting thing were some public opinion polls that I've seen that showed that space exploration even in the 1960's was never particularly popular.

It's interesting though how this bigger, better, faster, more idea of space as our future is pervasive in spite of evidence to the contrary.

Blame Gene Roddenberry, George Lucas, and the writers of Doctor Who. Then there are the directors of Avatar, Aliens, and about a dozen other science fiction movies.

 

[twofish-quant]

There's no question that we could cause a mass extinction event if we set our minds to it.

It's been argued that we are causing a mass extinction event without even trying that hard.

http://en.wikipedia.org/wiki/Holocene_extinction

One reason that I don't think that it may be such a good idea to even try to make another planet suitable for human life is that we will be lucky if we just don't totally mess up this one.

 

[Ryan_m_b]

The other interesting thing were some public opinion polls that I've seen that showed that space exploration even in the 1960's was never particularly popular.

Hmm, interesting.

Blame Gene Roddenberry, George Lucas, and the writers of Doctor Who. Then there are the directors of Avatar, Aliens, and about a dozen other science fiction movies.

I think a lot of the blame lies with commentators and SF writers who baselessly extrapolated the huge advances in transport technology in the first half of the 20th century. When you go from first powered flight to landing on the Moon in 60 years it's easy but flawed to expect this trend to continue.

It's been argued that we are causing a mass extinction event without even trying that hard.

http://en.wikipedia.org/wiki/Holocene_extinction

One reason that I don't think that it may be such a good idea to even try to make another planet suitable for human life is that we will be lucky if we just don't totally mess up this one.

I don't think we have a hope in hell in making anywhere else suitable for life if we can't maintain and fix this planet to how we need and want. The technology and industry requirements are the same if not far easier for doing things on Earth.

 

[twofish-quant]

One citation for this is

“Evolving Public Perceptions of Human Spaceflight in American Culture” by Roger Launius

I think a lot of the blame lies with commentators and SF writers who baselessly extrapolated the huge advances in transport technology in the first half of the 20th century. When you go from first powered flight to landing on the Moon in 60 years it's easy but flawed to expect this trend to continue.

I have a book from the 1960's that explicitly puts in that claim.

There's also the fact that history is non-deterministic. There's little from a physics point of view that would have precluded us having the sorts of space stations that you see in 2001: A Space Odyssey. The space ships to Jupiter are a bit harder. But 2001 is an interesting movie because it was how people in 1968 saw 2001, which tells you a lot about 1968.

 

[H2Bro]

One reason that I don't think that it may be such a good idea to even try to make another planet suitable for human life is that we will be lucky if we just don't totally mess up this one.

Distinctions about 'bad' or 'good' come from living things. So, is it 'bad' to mess up a planet that does not have life?

In the process of messing up this planet we learn a great deal about how it works. It's a terrible way to go about learning something, but having done so, would you willingly for-go the benefits derived from research that, when initially proposed, seems abominable?

And by research I mean 'lets see what happens when we pump gigatons of toxic waste into a perfect garden of eden.'

regardless of the blame or fault that led us into the current situation we might be wise to take what knowledge results and turn it to our advantage. i.e. attempt to set up alternative ecosystems now that we know at least one way to totally screw them up.

Indeed, the potential payoffs of attempting to terraform another planet only go up as the condition of this planet gets worse. Whether the risks go up as well depends on whether you think lifeless planets are valuable as-is in a situation where our own planet is uninhabitable.