Early Romans named the dazzling white planet Venus after their goddess of love and beauty. Although Venus is sometimes called Earth's sister planet because it is about the same size, composition, and age as Earth, conditions there are drastically different. Its atmosphere, formed from gases expelled during millions of years of volcanic activity, is mostly carbon dioxide, with miles-thick layers of sulfuric acid clouds circling the planet with hurricane force. The atmosphere is so dense that surface pressure is 90 times that on Earth, making life as we know it impossible and destroying landed spacecraft within an hour. Venus exists in a perpetual greenhouse effect that makes it the hottest planet in the Solar System, even hotter than Mercury despite being twice as far from the Sun, and it rotates east to west so slowly that a day lasts longer than a year. From Earth it appears white because sunlight reflects off its dense cloud cover, but on the surface it appears orange because the carbon dioxide atmosphere filters blue from sunlight. During the space race from the 1950s to the 1990s, the Soviet Union attempted 32 missions to Venus and America made 9 attempts, 8 of them successful. Major milestones included Mariner 2's 1962 flyby of another planet, Venera 3's 1965 crash landing, Venera 7's 1970 transmission from another planet to Earth, Mariner 10's 1974 gravity-assist flyby on its way to Mercury, Venera 9's 1975 orbit and soft landing, and NASA's Magellan mission from 1990 to 1994, which mapped the entire Venusian surface with radio waves while remaining in orbit. Most features on Venus are given female names.