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PostPosted: Wed Jul 31, 2019 5:53 am 
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Joined: Sat Sep 01, 2012 2:44 pm
Posts: 203
Location: Colorado
Questions:

When does a super-Earth become a water world? Is it a mass/radius combination that creates this possibility?

Obviously it has to be at a distance from the star where the temperature will allow liquid water but if it has a larger denser atmosphere, could that pressure change the temperature at which water is liquid?


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PostPosted: Thu Aug 01, 2019 4:39 pm 
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Joined: Thu Jul 12, 2012 10:11 pm
Posts: 362
Location: Near Frankfurt, Germany
FWIW, here´s the minimum, average and maximum surface gravity (rounded to nearest 0.01g) for each size code:

Size 1: 0.03g - 0.09g - 0.15g
Size 2: 0.08g - 0.20g - 0.33g
Size 3: 0.11g - 0.30g - 0.49g
Size 4: 0.20g - 0.45g - 0.70g
Size 5: 0.25g - 0.56g - 0.88g
Size 6: 0.38g - 0.75g - 1.13g
Size 7: 0.44g - 0.88g - 1.31g
Size 8: 0.60g - 1.10g - 1.60g
Size 9: 0.68g - 1.24g - 1.80g
Size A: 0.88g - 1.50g - 2.13g
Size B: 0.96g - 1.65g - 2.34g
Size C: 1.20g - 1.95g - 2.70g
Size D: 1.30g - 2.11g - 2.93g
Size E: 1.58g - 2.45g - 3.33g
Size F: 1.69g - 2.63g - 3.56g
Size G: 2.00g - 3.00g - 4.00g
Size H: 2.13g - 3.19g - 4.25g
Size J: 2.48g - 3.65g - 4.73g
Size K: 2.61g - 3.80g - 4.99g
Size L: 3.00g - 4.25g - 5.50g

There are greater "jumps" going from odd to even size digits than going from even to odd because the size bonus to the 2d6 roll is rounded down. I might want to either not round it, or double all numbers (while reducing the 0.0125 multiplier to 0.00625) to use the full size digit as a bonus, so there there is a smoother progression from digit to digit.

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PostPosted: Sat Aug 03, 2019 1:48 pm 
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Joined: Mon Dec 02, 2013 1:43 pm
Posts: 351
Location: Queens, NY
hiro wrote:
Questions:

When does a super-Earth become a water world? Is it a mass/radius combination that creates this possibility?



By "water world" do you mean what EDG calls a panthalassic world, where the boundary between surface and atmosphere is a blur?

If that's your Q, I asked about that in a different thread somewhere, and I think a world could be a panthalassic world under specific conditions:

1) Mass maybe 4+ total earth masses, with 2+ earth masses comprised of water. Like, lots of friggin' water, man. I'm not exactly sure how big it needs to be, but definitely bigger than Earth.

2) A density that would fit. If Earth as it is has a density of 5.52 g/cm3, and you add another whole earth mass of water, you get a density of 3.25 or so. If you're rolling randomly for density, a high mass world with low enough density might fit this classification.


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PostPosted: Sat Aug 03, 2019 1:51 pm 
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Joined: Mon Dec 02, 2013 1:43 pm
Posts: 351
Location: Queens, NY
Agemegos wrote:
Cyborg IM1 wrote:
look at Mercury, denser than Venus and Mars.


My info might be out of date, but I recall something about Mercury being a freak outlier, that it was a larger world, but its rocky outer shell might have been stripped by a collision similar to how the moon was formed.

Regardless, I suppose any random density generator should allow for the possibility, however slim.


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PostPosted: Sun Aug 04, 2019 5:37 am 
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Location: the Retirement Coast, NSW, Australia
Matt Wilson wrote:
Agemegos wrote:
look at Mercury, denser than Venus and Mars.


My info might be out of date, but I recall something about Mercury being a freak outlier, that it was a larger world, but its rocky outer shell might have been stripped by a collision similar to how the moon was formed.

Regardless, I suppose any random density generator should allow for the possibility, however slim.

The thing is that the sample size is so small that once you throw out a "freak outlier" there aren't enough data left to fit a curve.

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PostPosted: Mon Aug 05, 2019 3:49 pm 
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Location: Texas, USA
Thanks for all the advise. :)

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