Suppose that in 2014, the Hubble Space Telescope discovers a series of planets with the following characteristics moving around
a star resembling our Sun: spherical, solid surfaces; mean densities about four times that of H2O; radii about 4000 km; low-density atmospheres. How would these planets be classified in terms of our solar system?
These planets would be classified as rocky planets because of their small diameter, relatively high density, and low-density atmospheres. The profile of such a planet is, in fact, very similar to that of Mars, which has a radius of just under 4000 km, an atmosphere thinner than that of Earth and a density also less than that of Earth.
Gas giant planets have much lower densities and much larger dimensions than the terrestrial planets as more gravity is needed to retain their massive, gaseous atmospheres.
The main reason why Earth is warmer at the equator than at the North and South Poles are thats where the sunlight shines at a lot of times. The sunlight never really shines directly at the North and South Poles like it does with the equator.
