first robotic space probe mission to Venus and any planet was Venera 1 of the Soviet Venera program launched in 1961, though it lost contact en route. The first successful mission to Venus (as well as the world's first successful interplanetary mission) was the Mariner 2 mission by the United States, passing on 14 December 1962 at above the surface of Venus and gathering data on the planet's atmosphere. On 18 October 1967, the Soviet Venera 4 successfully entered as the first to probe the atmosphere and deployed science experiments. Venera 4 showed the surface temperature was hotter than Mariner 2 had calculated, at almost , determined that the atmosphere was 95% carbon dioxide (), and discovered that Venus's atmosphere was considerably denser than Venera 4 designers had anticipated. The joint Venera 4–Mariner 5 data were analysed by a combined Soviet–American science team in a series of colloquia over the following year, in an early example of space cooperation. On 15 December 1970, Venera 7 became the first spacecraft to soft land on another planet and the first to transmit data from there back to Earth. In 1974, Mariner 10 swung by Venus to bend its path toward Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speeds in the Venusian atmosphere. This was the first interplanetary gravity assist ever used, a technique which would be used by later probes, most notably Voyager 1 and 2. In 1975, the Soviet Venera 9 and 10 landers transmitted the first images from the surface of Venus, which were in black and white. In 1982 the first colour images of the surface were obtained with the Soviet Venera 13 and 14 landers. NASA obtained additional data in 1978 with the Pioneer Venus project that consisted of two separate missions: Pioneer Venus Orbiter and Pioneer Venus Multiprobe. The successful Soviet Venera program came to a close in October 1983, when Venera 15 and 16 were placed in orbit to conduct detailed mapping of 25% of Venus's terrain (from the north pole to 30°N latitude). Several other missions explored Venus in the 1980s and 1990s, including Vega 1 (1985), Vega 2 (1985), Galileo (1990), Magellan (1994), Cassini–Huygens (1998), and MESSENGER (2006). All except Magellan were gravity assists. Then, Venus Express by the European Space Agency (ESA) entered orbit around Venus in April 2006. Equipped with seven scientific instruments, Venus Express provided