VENERA

any of a series of unmanned Soviet planetary probes that were sent to Venus. Venera 2 (launched in 1965) flew to within 25,000 miles (40,200 km) of Venus in February 1966, and Venera 3 crash-landed on its surface the following month, becoming the first spacecraft to strike another planet. Venera 4 (1967) analyzed the chemical composition of Venus' upper atmosphere and provided the scientific community with the first direct measurements for a model of the planet's atmospheric makeup. Venera 5 and 6 (1969) made similar soft landings on Venus, but ceased transmitting data before reaching the surface because of the extreme heat and pressure of the planet's atmosphere. Venera 7 (1970) and Venera 8 (1972) detected the occurrence of certain long-lived radioactive isotopes (chiefly uranium and thorium) on Venus' surface. Venera 9 and 10 (1975) sent back the first closeup photographs of the planet's surface; these images showed that certain parts of Venus were covered with sizable sharp-edged rocks and others with fine-grain dust. Venera 11 and 12 (1978) measured the chemical components of the planet's lower atmosphere.