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The first artifical satellite in space.
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The first human in space.
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He was the first U.S. citizen to be in space.
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The first U.S. citizen to orbit Earth.
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The final stage of the U.S. program to reach the Moon and Neil Armstrong is the first man to walk on the Moon.
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Obtained the first good images of the surface of Mercury.
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Imaged craters, lava, domes, and great rifts, or cracks, on the surface of Venus.