data suggested that water, if it had been present, had leaked from the planet long before. This conclusion was unexpected considering the thick Venusian clouds. Because of the negligible humidity, the sugar lock system, employed on Venera 4 in case of a water landing, was abandoned in subsequent Venus probes. The mission was considered a complete success, especially given several previous failures of Venera probes. Although the Venera 4 design did allow for data transmission after landing, the Venera 3–6 probes were not built to withstand the pressures at the Venusian surface. The first successful soft landing on Venus was achieved by Venera 7 in 1970. See also List of missions to Venus References Cited sources Venera program Derelict landers (spacecraft) Spacecraft launched in 1967 1967 in the Soviet Union 1MV