I know you hung up my line--Star 69

[cyrano]

This is a request for advice from my science-smart friends. Please take a moment, help me get a reality check on the setting for my FireFly OryCon one-shot.


The planet is covered in water--about 15 meters deep, in general. I think this means an old planet. If so, what are the general qualifications of a planet of that age? I'm thinking high salinity in the water, and good sized waves that travel the surface of the planet. The installment on the planet is a mining colony, sunk into the ocean floor and surrounded by large metal breakwaters to protect it from the waves.

The social economy is standard Victorian Empire--there are the lower classes who work in the mines, on the docks, in the desalinization plants, eat the fish poisoned by the byproducts of the mining and live nasty, short brutish lives. The upper classes exploit the lower, live high above in the towers and eat kittens because they're so evil.

Comments

[wildpaletz.livejournal.com]

I can't answer a lot of this because it's not really my area. I have, however, been reading a few random things here and there about planetary geology so I can have a basis for conversation with the folks who do do that sort of thing (should I be called upon to do so).

So, on my limited, limited knowledge:
a) There aren't any known water worlds. This is ok, it means you get to play with fiction more.
b) There are worlds that have been theorized to be all ice.
c) Theoretically, if you have a planet that would have been all ice, and it's got a pleasant tempurature, the water could be liquid. Or, rather, because it's only liquid for a limited temp range, it's probably icy at the poles and there's a lot of water vapor in the atmosphere.
d) So it probably rains a lot too.
e) I'd guess it'd be deeper than 15 meters. I am not sure why I guess that. Probably having to do with ice and stuff. And we have a lot of places here that are deeper than that. This guess doesn't negate the idea of having mining in the floor or even having high salinity, but it does mean there's interesting pressure differences, potentially isolated groups of people lower down, etc.
f) If it's a water world, in addition to fish, you could have a whole complex fauna and flora system in the water. W00T!
g) And probably desalinization to get drinkable water. A weak point for rebel action, possibly. Water, water, everywhere, but not a drop to drink.
h) I read recently a hypothesis that Mars lost its water because it doesn't have a nice, friendly, protective, all-encompassing magnetic field like Earth does. So maybe your planet would have one too.
i) Hell if I know if that means it's an old planet or not. Why would it be old? Maybe it just has a lot of water, as opposed to being a gaseous fun ball. Or maybe it's a moon, even. A honkin' big moon with almost 1 g.
j) I'm guessing too that a planet of all water, if it has good winds, would build up some hella big waves, ayup.

Some of the stuff about water I learned from here: http://www.pbs.org/wgbh/nova/mars/essential.html

The rest is "ex recto" as they say.

I have an anal orifice too!

[space-parasite.livejournal.com]

So please don't take this as more authoritative than the foregoing.

a) There aren't any other known habitable or even particularly Earth-like planets, so sure, go for it!

b-c) If you're thinking of something like Europa, note that melting it all would get you an ocean hundreds of kilometers deep. If you had a Europa the size of Earth and melted it, you'd have more than a thousand kilometers of water.

d) Depends on the temperature, I think, for evaporation rates. I mean, Earth is already 3/4 water; being all water wouldn't make that much of a difference.

e) See above, but of course there's no reason to think that you couldn't have planets with intermediate amounts of water, so 15m average depth seems plausible to me. However, on Earth the greatest difference in elevation is like 20 000m, so even on a fairly old and worn-down planet I'd expect at least a couple of thousand meters difference. Up to you whether that means going from a depth of 15 meters to an altitude of 1985m, or from a depth of 2015m to shallows of 15m.

f) Sure, we've got one on Earth! You need something to get energy from the environment and turn it into fish food anyway, so you can't really have less than fish + seaweed. (Although a really simple ecosystem would probably be all single-celled plankton things.)

g) Yah, desalinization, but if you have interstellar travel, even with the Handwave Drive, you have enough energy that distilling water isn't a problem. Unless you want to add more handwaves to explain why things are just like now only with interstellar travel, but if you do that, I might not love you anymore.

h) My understanding is that it would actually be ozone that protects against water loss, by absorbing the UV that would otherwise go into splitting water into H2 (which promptly escapes into space) and O. However, lack of a magnetic field might keep ozone from accumulating (it all gets broken down by aurorae? dunno). Anyway, so far as I know, the processes by which Earth generates its magnetic field are very not well-understood, so you can probably pick whatever value you want for your planet regardless of its age.

j) Yep! And I think all you need for hurricanes is water and planetary rotation (coriolis force), so you could have hurricane-like phenomena, waterspouts, etc.

Hopefully I have been more helpful than antihelpful.

heh.

[wildpaletz.livejournal.com]

A couple comments -- mostly I agree on the basis of "sure, yeah!"

--Desalinization -- I'm sure they have the tech for that. I was just mentioning it because if he had characters who wanted to screw with something, and if water purifying was centralized, well, that's something that could be screwed with that isn't as obvious as, say, making a big hole in an underwater habitat.

--The magnetic field / water thing isn't actually ex recto. I got it from here:
http://science.nasa.gov/headlines/y2001/ast31jan_1.htm

The idea (not proved, mind you) is that solar winds rip away the water, rip rip!

That being said, doesn't matter too much for Cyrano's world, because of what you said -- poof, the planet has a magnetic field, 'cuse why not.

Re: heh.

[space-parasite.livejournal.com]

Well, my point with desalinization is that it would be easy enough to do that they could reasonably have or easily rig up redundancy. Although as another commenter implied, that may be too much thinking for the TV SF genre. (Or, it could be a plot point, if any of the players seems likely to think of that sort of thing.)

My reading of the NASA article is that the solar wind rips away the atmosphere entirely, which makes perfect sense. The UV-splitting-water-so-the-hydrogen-escapes thing is a way to have the planet depleted specifically in water, while still having an Earth-like atmosphere. So we aren't disagreeing!