Assessment of Extraplanetary Bases

[GregA]

Then it is only a naming difference: When you build a colony in Phobos or an asteroid, then I would not call it orbital colony, because its on a celestial body. But I see, that this can be seen different. I was only arguing against colonies that are build into nowhere with the need to get the ressources from somewhere else or even the earth to build it.

Yeah, A lot has been written about this. Closed biological systems are all basically coffins. If we are interested in realism, humans are essentially trapped on earth. We have to think about concepts like post-humanism (is that concept banned on this website, I don't even know, it seems like it would trigger some people...), genetically converting humans into martians, uploading and matryoshka brains if you want to live on an orbital colony. The best, most realistic, ideas all seem centered around the concepts of terraforming.

But as a species we can't even get our heads around a 30ppm issue with the atmosphere, here on planet earth. How do we even begin to contemplate a 1 million ppm issue with an alien atmosphere...

[sndrtj]

Stop talking about things you know nothing about, it's pretty clear you don't even know the difference between acetylcholine and acetylcholinisterase-this is high-school level stuff. Given the major differences in biological pathways we already have between organisms, and how easy you're suggesting producing lethal toxins by chance is, why isn't the world already completely full of poisons? There's just as much reason for an alien organism to produce Sarin as there is for most plants to, given they don't utilise acetylcholinisterase; why hasn't your scenario already come to pass?

I guess you're taking his point a wee bit too literal. What Greg is pointing is a true and existing risk. Remember that paper from Science a few years ago that caused a slight fuzz with its supposedly arsenic-utilizing prokaryotes? Well.. turned out they were in stead merely resistant to arsenic, and used plain phosphate instead, but the idea itself is quite relevant for astrobiology: on an alien world where there is very little phosphate but ample arsenic (and assuming it has life), evolution would probably have used arsenic, which is very toxic to almost any Earth life. And there you'd have it: toxic lifeforms to us. The soup of alien metabolites is sure to contain some molecules known to man, and not all of those will be harmless (they will probably have completely different functions in alien life forms than on Earth, and that's exactly what makes it dangerous).

[kStrout]

Then it is only a naming difference: When you build a colony in Phobos or an asteroid, then I would not call it orbital colony, because its on a celestial body. But I see, that this can be seen different. I was only arguing against colonies that are build into nowhere with the need to get the ressources from somewhere else or even the earth to build it.

No no, the colonies wouldn't be inside Phobos, we would mine Phobos and then use the raw materials to build colonies from scratch in martian orbit. And it wouldn't make any sense to build colonies from earth materials when you can mine the moon and import those materials to LEO(which is a GREAT place to build colonies because the van allen belts mean you need almost no shielding) at less than the cost of launching them from earth, but I see your point, no sense building colonies in orbit around Venus.