The correct answer is x Earth. Key Points - The eight planets of our Solar System vary widely, not only in terms of size but also in terms of mass and density. - The 4 inner planets are closest to the Sun are called terrestrial planets, meaning they are composed primarily of silicate rocks or metals and have a solid surface. - On these planets, density varies the farther one ventures from the surface towards the core. - Earth: - Earth has the highest density of any planet in the Solar System, at 5.514g∕cm3. - This is considered the standard by which other planet's densities are measured. The combination of Earth's size, mass, and density also results in a surface gravity of 9.8m∕s2. - The 4 outer planets are known as gas giants which are composed primarily of hydrogen, helium, and water existing in various physical states. - While these planets are greater in size and mass, their overall density is much lower.
