Color image (Mariner 10)

Mercury - The Planets


Mercury is the closest planet to the Sun, and the second-smallest planet in the Solar System. Mercury ranges from −0.4 to 5.5 in apparent magnitude, and its greatest angular separation from the Sun (greatest elongation) is only 28.3, meaning it is only seen in twilight. The planet remains comparatively little-known: the only spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, which mapped only 4045% of the planet's surface.