First planetary flyby with data returned

NASA's Mariner 2 conducted the first successful planetary flyby, returning valuable data from Venus. This mission marked a pivotal advancement in space exploration, as it was the first time that a spacecraft successfully gathered and transmitted scientific information from another planet. The Mariner 2 spacecraft was launched with the primary objective of studying Venus, which had long been a subject of interest due to its proximity and similarities to Earth. The mission provided critical insights into the planet's atmosphere, surface temperature, and other characteristics, significantly enhancing our understanding of planetary science. The data collected indicated that Venus had a high surface temperature and a dense atmosphere, composed mainly of carbon dioxide, which was a crucial finding for future studies of planetary atmospheres and climate.