Mariner 1, 2
Mariner 2 was the world's first successful interplanetary spacecraft. It became the first spacecraft to flyby another planet on December 14, 1962 when it passed within 34,833 kilometers from the surface of Venus. During its flyby, Mariner 2 measured the temperatures of the clouds and surface of Venus as well as fields and particles near the planet and in interplanetary space. It discovered that Venus lacks a strong magnetic field and radiation belts, and that Venus' surface temperature was over 400 deg C. Contact was lost January 3, 1963 when the spacecraft was 86.9 million kilometers from Earth. An identical sister vehicle, Mariner 1, was lost in a launch failure prior to the launch of Mariner 2.
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