Heidi T. answered • 10/08/21

Experienced tutor/teacher/scientist

To solve this, assume that all planets are spherical. This assumption and the radius of the planet allows you to calculate the volume of a planet, V = (4/3) π r^{3}. R_{E} = radius of earth ( in cm) and M_{E} = mass of earth (in grams)

Density, ρ = (Mass / Volume)

So the mass of each planet is given in terms of the mass of earth. multiply the mass of earth by the number to get the planet mass. In the same way, find the planet radius by multiplying the number by the radius of earth. Solve for the volume. Then you can calculate the density.

The density allows you to determine the composition of the planet.

The density of water = 1 gm/cm^{3}

So if the density of the planet is close to the density of water, The planet is made mostly of ice.

If the density of the planet is < 1, it is a gas giant.

If the density of the planet is > 1, it is rocky/terrestrial (densities of rocks typically range from 2-6 gm/cm^{3})

Heidi T.

You can also find the density of the planet relative to the density of earth... if the radius of the planet is r = C* RE, where C is the scale factor, then V = C^3 * VE; then the mass is m = A * ME, and the density = (A/C^3)(ME/VE) = (A/C^3)*[density of earth]10/08/21