Astronomy Picture of the Day . ... Credit: John Harms Explanation: The Full Moon and a brilliant, ruddy Mars will share the sky tonight. ... Mars is so bright because it is near opposition, opposite the Sun in Earth's sky and near its closest approach to planet Earth. But Mars is not nearly as bright as the Moon, also opposite the Sun tonight. In this striking preview of tonight's sky show, backyard astronomer John Harms was able to photograph an almost Full Moon near Mars last month. ...