... would be at the next opposition, two Earth years, or roughly four Martian years, hence. The Martians knew this, because their teams of telepaths were able to catch at least some of the thoughts of Earthmen, enough to know their plans. Unfortunately, at that distance, the connection was one-way. Mars could not ask Earth to hurry its program. Or tell Earth scientists the facts about Mars' composition and atmosphere which would have made this ... — Earthmen Bearing Gifts • Fredric Brown
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