Nowhere else in our solar system is there a planet that is habitable. Venus and Mars are the two planets closest to our Earth. Venus, closer to the Sun and about the same size as Earth, has an atmosphere where the temperature reaches about 870 Degrees F (about 470 Degrees Celsius), because of a runaway Greenhouse Effect. It has clouds of sulfuric acid, and an atmosphere of mainly carbon dioxide and nitrogen. Mars, which is smaller and whose distance from the Sun is more than Earth's, has little or no atmosphere, because, with its smaller size its gravity is not strong enough to hold on to an...