Here is a sentence from the psychologist Paul Ekman's book Emotions Revealed: The western hospital with all its facilities made the experience unreal, as though she has been on Mars and then returned to Earth. Here Ekman is talking how a Papua New Guinean woman, who didn't show any sign of sadness at the loss of her child at the hospital, burst into tears and seemed to be overcome with grief upon arrival at her village and when seeing her fellow villagers. My questions are 1) Why not use the article "the" before words like Mars and Jupiter? 2) should we always use the article "the" when we talk about our planet earth (and the sun also)? 3) why is "earth" capitalized here? And once it is capitalized, the "the" must be dropped?