Absolute smallest viable size for a colony.

[Telok]

Not finding any reports of anything on Titan beyond organic molecules. In chemistry speak that means "has carbon-hydrogen bonds or carbon rings/chains". Which does happen without life.

For a viable colony I'd prefer to slightly violate the "no stuff" part of the op. Grab a major natural history museum during a busy day, building and everything/everyone inside, then plop it down somewhere near a warm temperate river delta but not in a flood zone. For extra security take the biggest industrial history museum of the same nation/language group at the same time and put it down in the same place. You'll get tools, supplies, shelter, mostly the same culture & language but with some diversity, and the population now skews both younger and more educated with experts in document & knowledge preservation.

[Eldan]

I can't remember off the top of my head if it's four or five meteorites, but they've all shown marks of life.

The stuff from Titan is more interesting, to me at least. Titan is a much better candidate for colonization than Mars.

Again, I read every news article on Titan and have for years, and I'm a biologist. If there was extraterrestrial life confirmed or even strongly suspected, it would be in every newspaper in the world. IF you don't have any sources, I don't believe you.

[Fyraltari]

I'm not so sure about the viruses. Sure, it would be silly to assume the species of another world just happen to have DNA equivalent to our own. On the other hand, it's equally silly to assume they don't.

No, it’s not. To assume, until proven otherwise, that life developed the same way on another planet is to claim to know how the mechanism behind the apparition of life works which we don’t.

To assume, until proven otherwise, that life developed differently is to admit that we don’t know how it works and that there is no known reason for it to only work one way.

And personally, I lean towards the first kind of silly. I think life, universally, is self-ordering. I think if we find an earthlike world, it will have earthlike life. Including near-identical DNA. But that's easy to say, since we may never know the truth of it. Unless we conveniently find life somewhere in our own solar system, that is.

Considering the diversity of paths life took on our one planet from a single ancestral organism, I find it unlikely that other forms of life, developed in parallel on other planets would be even close to what we know.

[Kaptin Keen]

No, it’s not.

Yes, it is. We don't know either way. But there is substantial evidence to support an 'ordering' of stuff. Not being religious - but you're not going to hear anyone claim atoms are different elsewhere, right?

So .... where do you draw the line? Atoms are the same, but molecules are not? Or is it only the specific molecules, like DNA?

You say life here took different paths. Well, so it did. Are any of those paths non-DNA? No. They're not. And different paths have lead to suspiciously similar results. And some different ones, sure. But I'm not saying we'll magically find identical life elsewhere.

What I'm saying is that evolution works like this: If what you need is to grab stuff, opposable thumbs are great. If you need to keep warm, hairs are great. And so on - for basically every design decision mother Earth coughed up.

In a similar environment - similar solutions will work.

But I'm basing this on nothing but opinion. You're more than welcome to disregard it out of hand.

[Fyraltari]

Okay so working from less different to more different:

-one given problem may have many different solutions not all of which are explored. For example in order to fly, birds, insects, bats and flying squirrels all developed completely unrelated means. Are there any other way this could be accomplished? We don’t know.

- There are a huge varieties of environments. Earth used to be hospitable to megafauna for example and now it isn’t. Completely different bacteria evolved on the various continents, etc. Etc. What kind of problems would extra-terrestrial environments caused that weren’t seen in Earth? We don’t know. Maybe creatures that breathe nitrogen or whatever.

-Every single one organic chemical not made in a lab is left-justified. Every single experiment on the subject shows that left-justified and right-justified molecules are as likely as the other to form. What would a right-justified based tree of life look like? What’s for sure is that its biochemistry would be incompatible with ours.

-Desoxyribonucleic acid has the ability to create copies of itself, that’s the basis of what we call « life ». Is it the only molecule that can do that? Some amino acids that our ancestors didn’t use?We don’t know. Silicium has properties that are very close to carbon, the main component of DNA. What would a silicium-based lifeform look like. Would we even recognize it as alive if we encountered it?


Life as we know it is the result of an unknowable number of choices that happened during our evolution as the result of a very narrow set of circumstances. To assume that it is the only path that leads somewhere is much more presumptuous in my eyes than to assume it isn’t.

Edit: about the fact that there are no non-DNA based life on Earth. There’s such a thing as a niche. Once something occupies it nothing can take that place. Once left-DNA-based life established itself it probably became impossible for any theoretical non-DNA-based/right-DNA based life to evolve because the one that got there first gobbled up the resources and started modifying the environment (the high amount of O2 in our atmosphere is a consequence of the development of life, not a cause).

[Kaptin Keen]

You're saying - as far as I can tell - not a single thing that contradicts my assumption that nature is self-ordering, and a few that obviously support it. And you're conveniently avoiding my primary point that evolution picks something that works, and for similar circumstances it's silly to assume a dissimilar solution.

Ie. on an Earth-like planet, you'll find Earth-like life. Maybe. We can't know. Maybe on an Earth-like planet, for random and undisclosed reasons, we'll find entirely different life. But why you'd assume that is entirely beyond me.

[Fyraltari]

What I’m saying is that Occam razor says that the safer bet is the one with the fewest assumption. Proposition « Life on another planet will be mostly similar to life here » requires more assumption both about environment and the mechanism of life itself than « life in another planet will be mostly different from life here. » Therefore, absent evidence for either case, the second one is the more reason able assumption.

Also I am not sure what you mean by nature being « self-ordering ». Order is mostly subjective (« what is chaos to the fly is order to the spider » and all that) and the Second Law of Thermodynamics means that what we recognize as orderly is in constant diminution.

[factotum]

In this specific scenario we have been told that the environment is abundant in creatures humans can eat, so it's a pretty safe assumption that their biology is similar to ours.

They might even be transplanted creatures from Earth, just like the humans are.

[Kaptin Keen]

What I’m saying is that Occam razor says that the safer bet is the one with the fewest assumption. Proposition « Life on another planet will be mostly similar to life here » requires more assumption both about environment and the mechanism of life itself than « life in another planet will be mostly different from life here. » Therefore, absent evidence for either case, the second one is the more reason able assumption.

Also I am not sure what you mean by nature being « self-ordering ». Order is mostly subjective (« what is chaos to the fly is order to the spider » and all that) and the Second Law of Thermodynamics means that what we recognize as orderly is in constant diminution.

Well - if you're paying attention, what I said was the picking one silly assumption over another silly assumption is meaningless. Then I go on to pick one regardless, and explain why I like one set of nonsense over another.

Self-ordering is simplicity itself: Evolution is a filter which sorts working solutions into one pile, and not-working solutions into ... well, no pile. Order and chaos has nothing to do with it.

[Fyraltari]

In this specific scenario we have been told that the environment is abundant in creatures humans can eat, so it's a pretty safe assumption that their biology is similar to ours.

True.

Well - if you're paying attention, what I said was the picking one silly assumption over another silly assumption is meaningless. Then I go on to pick one regardless, and explain why I like one set of nonsense over another.

Except one is the more reasonable pick. And that’s not yours.

Self-ordering is simplicity itself: Evolution is a filter which sorts working solutions into one pile, and not-working solutions into ... well, no pile. Order and chaos has nothing to do with it.

Great, so that tells us absolutely nothing about the number of solutions.
Edit: also that’s natural selection.

[Kaptin Keen]

Except one is the more reasonable pick. And that’s not yours.

Yes it is. Ready to give this a rest?

Great, so that tells us absolutely nothing about the number of solutions.
Edit: also that’s natural selection.

It doesn't need to. And yes, it is.

[Rockphed]

In this specific scenario we have been told that the environment is abundant in creatures humans can eat, so it's a pretty safe assumption that their biology is similar to ours.

Their biochemistry produces left handed amino acids at least.

[Eldan]

And DNA not based on Arsenic:
https://www.nationalgeographic.com/n...science-space/

(Yes, that one is real.)

[Fyraltari]

And DNA not based on Arsenic:
https://www.nationalgeographic.com/n...science-space/

(Yes, that one is real.)

[Vinyadan]

The DNA based on arsenic theory was undermined that same year, though.

[Poldon]

Order is mostly subjective (« what is chaos to the fly is order to the spider » and all that) and the Second Law of Thermodynamics means that what we recognize as orderly is in constant diminution.

Maybe I'm misinterpreting your meaning here, but lifeforms increase thermodynamic order all the time. Your cell membrane is a structure with high order. The trick is that this is local. The order of the system must decrease, but the local may increase, as long as there is a corresponding greater decrease elsewhere. One theory for the membrane is that it decreases the order of the water molecules around it by disrupting the polar bonds between the water. The water's increase in entropy(disorder) is greater than the hydrocarbons' decrease.

Life orders itself. The creation of complex molecules inside your cells is an increase in order. We just have to breakdown order elsewhere to make it work. Digestion is a good example.

Order is not subjective at all. One simply has to look at chemical reactions and their various properties. Larger-scale interpretation becomes more difficult, of course, but just because we can't reliably interpret something doesn't make it subjective.

If I've misinterprested your words, then consider this a tangent into the world of thermodynamic biochemistry (based on my old memories of old classes).

[Fyraltari]

Yes life tends toward chemical order. Nature does not. That's why all life eventually fails to function.