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I want to know how deep the oceans of my super-Earth can plausibly be. Is there any way to calculate the depth of my oceans? Here are the characteristics of my planet to help with the calculations:

  • Mass = 3.61 Earth Mass ($2.16 \times 10^{25}$ kg)

  • Gravity = 1.740933642 g (17.08 m/$\textrm{s}^{2}$)

  • Moon Mass = 0.23 Moon Mass

  • Moon Gravity = 0.56 g (5.46 m/$\textrm{s}^{2}$)

  • Moon Orbital Distance = 80939 km

Also, this article summarised that super-Earths that are Waterworlds can become terrestrial with shallow oceans due to a hot stratosphere, and also I heard that large moons that are close to a planet can cause shallow seas.

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  • $\begingroup$ I think this one has been answered a few times. For an Earth-sized mass, you max out at around 600 miles, where the pressure is so high that it can't be liquid at any temperature. $\endgroup$
    – Robert Rapplean
    Commented Jan 1 at 0:15
  • $\begingroup$ I agree with @RobertRapplean's vote that this Q is a duplicate. I don't believe the specific celestial characteristics make the question unique. Looking up the chart of what pressure converts salt water to ice and performing the calculations vs. the planetary characteristics to determine pressure vs. depth are a good exercise for a worldbuilder. $\endgroup$
    – JBH
    Commented Jan 1 at 1:08
  • $\begingroup$ oh its too similar srry $\endgroup$
    – user107608
    Commented Jan 1 at 1:25
  • $\begingroup$ what i meant like is there any numbers to determine average depth $\endgroup$
    – user107608
    Commented Jan 1 at 1:26
  • $\begingroup$ Ah, ok. You're actually asking for how deep the trenches could be on your planet? I think that's a new and interesting question, but would be worded significantly different. We'd have to close this and make a new one, something like "How much surface variation can a rocky planet have between average continental plate height and abyssal trench depth?" You might want to post this on Meta to help figure out proper wording. $\endgroup$
    – Robert Rapplean
    Commented Jan 1 at 2:24

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The answer to your question depends on two factors:

  1. The surface gravity of the planet
  2. The amount of liquid water on the surface

The surface gravity defines the maximum height of the asperities on the surface, the stronger the gravity the lower the max elevation, and the amount of liquid water how much of that gap can be filled: the more liquid water, the more likely is to have deeper waters.

The moon doesn't have influence on the ocean depth, apart from the tidal excursion.

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