Mars Mars - Rotating Model Credit:Almond/NASA Mars is the fourth planet out from the Sun. It is also the second smallest planet in the Solar System after Mercury.
Earth Earth - Rotating Model Credit: Almond/NASA Earth is the third planet from the Sun. It is the largest of four rocky, or terrestrial, planets. It is the only place in the Universe where we know life exists.
Mercury Mercury - False Colour Rotating Model Credit: NASA, Johns Hopkins University Applied Physics Laboratory, Carnegie Institution of Washington.