On August 27, 1962, NASA launched Mariner 2 atop an Atlas-Agena rocket, kicking off humanity’s first successful voyage to another planet. Before Mariner 2, interplanetary space was largely speculative, clouded by theoretical hazards ranging from intense solar wind to dense cosmic debris. Mariner 2 transformed science fiction into hard data. Operating on a meager budget of solar wattage with computing power vastly outstripped by today's simplest microcontrollers, the probe survived an early guidance glitch to trek millions of miles toward Venus. Its microwave and infrared radiometers famously pierced the planet's thick atmosphere, shattering romantic myths of a lush tropical sister world and revealing a crushing, runaway greenhouse hellscape. Mariner 2 proved that robotic hardware could reliably navigate and communicate across the deep void, establishing the foundational architecture for all interplanetary exploration that followed.