On July 14, 1965, NASA's Mariner 4 made the first successful flyby of Mars, passing within 9,846 kilometers of the surface and transmitting 22 close-up photographs back to Earth. The images took 8.5 hours to transmit and revealed a barren, cratered landscape resembling the Moon — dashing popular hopes of canals, vegetation, or civilizations. Mariner 4 also measured Mars's atmospheric pressure at less than 1% of Earth's and detected no magnetic field. While the results were disappointing for those hoping to find life, the mission proved that interplanetary exploration was feasible and set the stage for the Viking landers, the rovers, and the ongoing search for evidence of past microbial life on Mars.
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