# Can a planet bigger than earth exist with same density but with more water proportionally and a lighter core?

By bigger, only the area of the crust is necessarily bigger. Core is necessarily lighter. Everything else could vary. Can it hypothetically exist?

• "Same density" is difficult to reconcile with "more water" and "lighter core". If you add water, or make the core lighter, wouldn't that alter the density? Commented Aug 22, 2021 at 0:23

$$\rho_1r_1=\rho_2r_2$$
where $$\rho_1$$ is the density of the first planet, which radius $$r_1$$, and $$\rho_2r_2$$ are the same but for the second planet, so if you want a larger planet to have the same gravity as earth then the density has to be lower. There are exoplanets that have lower densities than earth but have larger radiuses. below is a plot of mass vs radius, where the black dots are know exoplanets (unfortunately the units are Jupiter mass and radius, so it is not as easy to compare to earth) the earth is at the intersection of the red lines. The green curves are along constant density, where the higher density is the lower curve. The data came from this site