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Old 09-22-2013, 08:46 AM   #1
dataweaver
 
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Default Alternate Garden Worlds: Cytherians

In GURPS Space, an Ocean World is defined as a world where the conditions are right to allow for liquid water, and a Garden World is an Ocean World where life has appeared and converted the atmosphere into an oxygen atmosphere. The underlying assumptions here are that life requires liquid water, and that atmospheric oxygen is an important factor in its existence: life either produces it (flora) or consumes it (fauna). This follows directly from the fact that life on Earth uses a "carbon base in liquid water" model.

But then we get to the "Other Life and Other Minds" chapter, and specifically the "Other Chemistries" section, we're introduced to a number of speculative alternatives to carbon-in-water, which would depend on worlds with different kinds of liquid oceans: e.g., lipid molecules in a liquid hydrogen medium, carbon or nitrogen molecules in an ammonia medium, silicon-based molecules in a sulfuric acid medium, and so on.

Each such speculative biochemistry would have its own notion of what qualifies as an Ocean World; and if the life form breathes something other than oxygen, then its equivalent of a Garden World might have a different atmospheric composition as well — one that's possibly just as unstable without that kind of life to maintain it as an oxygen atmosphere is without the presence of oxygen breathers.

Of particular interest to me at the moment is a comment in the section about sulfur-based life, where it speculates that on a "slightly cooler Venusian world with lakes and seas of acid on the surface", conditions might be suitable to such a biochemistry. Terraforming Venus to carbon-in-water standards of life is a herculean task at best, and almost certainly a fool's errand; but might it be easier to "terraform" it for use by a silicon-in-sulfuric-acid based ecosystem? (Henceforth, I'll be referring to silicon-in-sulfuric-acid as "Cytherian life", from its meaning as an adjective "of or relating to Venus".) This could lead to an interesting science fiction setting, with Earthlings and Cytherians cohabiting the Solar System in a future where Cytherian visitors from another star system came to ours and set up shop on Venus. I'm thinking of something vaguely like Alan Dean Foster's Humanx Commonwealth, but with a vastly more alien "partner race" than the Thranx ever were.

(Besides: "silicon-based life" is a science fiction trope; but I don't think I've ever seen someone sit down and work out any implications of what it might really be like.)

So, what would be the parameters for Cytherian versions of Ocean and Garden Worlds? GURPS Space describes the temperature range for silicon/sulfuric acid life as being between 50°F and 600°F (283K to 587K); but those are obviously gross approximations. What would be the actual range of conditions that would allow for rivers, lakes, and oceans of sulfuric acid on a world?

And what would Cytherian life breathe? That is, what would be the Cytherian equivalent of an "oxygen atmosphere"? GURPS Space suggests fluorine and hydrogen sulfide as possible respiratory gasses; I'm inclined to go with one of those unless and until a better alternative is presented. But which one?

Let's say that you do end up with large bodies of sufuric acid on a planet: would they tend to have the same sort of impact on albedo that large bodies of liquid water do? That is, should a Sulfuric Acid Ocean World have a range of albedos based on hydrographic coverage the way that Water Ocean Worlds do?
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Old 09-22-2013, 01:08 PM   #2
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Default Re: Alternate Garden Worlds: Cytherians

H. Beam Piper's "Uller Uprising" has a chapter on silico-organic biochemistry that would help you, though I seem to remember the Ullers breathed fluorine. Apparently it's not copyrighted.

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Old 09-22-2013, 02:07 PM   #3
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Default Re: Alternate Garden Worlds: Cytherians

Breathing fluorine isn't a problem; it's a feature. If anything in Piper's setup is a problem for my purposes, it's the assumption of a somewhat colder temperature than Earth; I'm looking for a biochemistry that operates in an environment significantly hotter than Earth.

Still, an interesting read; thanks for pointing it out.
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Old 09-22-2013, 02:13 PM   #4
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Default Re: Alternate Garden Worlds: Cytherians

Silicone as in alternating carbon and silicon atoms works.
I have my own carbon "plastic" based aliens in sulfuric acid under a thick atmosphere This allows small amounts of coexisting liquid water at temperatures that would boil here.
There are some archaea that can survive pH 0 and even pure anhydrous sulfuric acid only goes to pH -1.
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