Viewed from superior planets, Earth goes through phases. Superior planets can be seen as crescents only from the vantage point of a spacecraft that is beyond them. When two bodies appear to pass closest together in the sky, they are said to be in conjunction . When a planet passes closest to the sun as seen from Earth and all three bodies are approximately in a straight line, the planet is said to be in solar conjunction. If a planet disappears behind the sun because the sun is exactly between the planets, it is said to be in occultation .
Superior planets can have only superior conjunctions with the sun.
At superior conjunction the outer planet appears in its completely illuminated full phase, whether it is on the same side or the far side of the sun. The planet is said to be at opposition to the sun when, at superior conjunction, both it and the Earth are on the same side of the sun. Opposition is a good time to observe an outer planet with Earth-based instruments, because it is at its nearest point to the Earth and it is in its full phase. Inferior planets can never be at opposition to the sun, from Earth's point of view. Occultations, transits, conjunctions, and oppositions offer special opportunities for scientific observations by spacecraft.