On August 27, 1962, NASA launched Mariner 2, an austere 447-pound framework of aluminum, solar panels, and scientific sensors bound for Venus. In doing so, humanity cast its first successful data link across the interplanetary void. Before Mariner 2, Venus was shrouded not just in opaque clouds, but in romanticized sci-fi fantasies of lush, primordial swamps. By transmitting microwave and infrared radiometer data back to Earth across tens of millions of miles, the probe stripped away the mythology to reveal a runaway greenhouse hellscape. Mariner 2 established the enduring paradigm of modern deep-space science: uncrewed, autonomous sentinels translating hostile physics into actionable telemetry. It transformed planetary exploration from passive observation behind telescope lenses into an active, data-driven discipline, proving our instruments could survive and report back from the deep frontier.