Solar system exploration is approaching a major turning point just as it is surpassing a major milestone. Fifty years ago, on Aug. 27, 1962, NASA launched the first successful planetary probe, Mariner 2, which visited Venus later in that same year. Regarded as both the evening and the morning star, Venus had long enchanted humans, and all the more so since astronomers had realized that it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view.
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