Definition: Aphelion: (opposite of perihelion) the point in its orbit where a planet is farthest from the Sun; when refering to objects orbiting the Earth the term apogee is used; the term apoapsis is used for orbits around other bodies.
Aphelion
From Nick Greene, for About.com
COMPARISON VIEW OF MARS CLOUD COVER - taken when Mars was near aphelion - Definition: Aphelion
NASA Goddard Space Flight Center (NASA-GSFC)Explore Space / Astronomy
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