Super Earth alien planet and its parent star and other planets, illustration. A super Earth is an extrasolar planet with a mass higher than Earth's, but significantly lower than the Solar System's gas giants. Uranus, the lightest gas giant in our Solar System, still has a mass 15 times that of Earth. The composition of super Earth planets is not known, although knowledge of their masses and radii provide clues. Planets not much more massive than Earth could be terrestrial: large, dense rocky bodies. Some may also be ocean planets, covered in water. Planets much more massive that these would retain a substantial atmosphere, and be classified as a gas dwarf.