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 Post subject: Panthalassic worlds
PostPosted: Thu May 16, 2019 1:23 pm 
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I couldn't find a thread specifically about these guys, so I'm gonna start one.

Evil Dr. G describes them in one thread as "a few earth masses of water on top of a rocky core".

So let's say minimum what... 3 earth masses total? 2.5-ish?

And then a density much lower than Earth, maybe 3.5 g/cm3? Or even lower than that?

Assuming both of those, you'd get a radius of maybe 10,000 km, (CT size C!) but a surface gravity (wherever the surface is) close to that of Earth. I think I recall something about a lack of clear boundary between surface and atmosphere.

I'm supposing all that water vapor in the atm will make things a lot warmer. Venus-like levels of greenhouse effect? As in a panthalassic world orbiting our sun would be a roasting nightmare in Earth's orbit?


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 Post subject: Re: Panthalassic worlds
PostPosted: Thu May 16, 2019 2:38 pm 
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I'd say they're usually 3-6 earth masses? Smaller ones are possible of course, but otherwise you got the details right. Things may get supercritical depending on the pressure so the boundary between ocean surface and atmosphere would be fuzzy.

Greenhouse effect and atm pressure would probably be high so yeah, it'd likely be a "steam greenhouse" world at the surface at least at Earth's distance. Might be more habitable in the Middle Zone though (between habitable and outer zone).

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 Post subject: Re: Panthalassic worlds
PostPosted: Thu May 16, 2019 8:06 pm 
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So instead of an "ocean world" (like Kamino in the Star Wars prequels) you´d get something closer to a miniature gas giant, except with water vapor instead of hydrogen, and as mentioned a lot warmer for the level of stellar radiation it receives?

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 Post subject: Re: Panthalassic worlds
PostPosted: Fri May 17, 2019 12:46 pm 
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Location: Queens, NY
Think the atmosphere would be dense enough to float a city in, in the style of those proposed Venus habitats? I suppose escape velocity would be tougher than on Venus, making a non-contragrav settlement less appealing, huh?

So many places in space that I'm content viewing from a distance.

Thanks for the feedback.


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