Mariner 2 was a robotic spacecraft launched by NASA on August 27, 1962. It was the first successful mission to Venus, providing valuable data about the planet's atmosphere and surface temperature. Mariner 2 flew within 34,773 kilometers (21,645 miles) of Venus on December 14, 1962, and transmitted information back to Earth. The spacecraft measured the planet's temperature, which was found to be around 427 degrees Celsius (800 degrees Fahrenheit), indicating a hot, inhospitable environment. Mariner 2 also detected a lack of a magnetic field and provided insights into Venus's atmospheric composition, paving the way for future exploration of the planet.