The Venus earth'sin twin

T h e   v e n u s    e a r t h ' s    t w i n

Venus is the second closest planet to the Sun. Telescopes reveal little about the planet due to global cloud cover. Venus' mass and volume are quite similar to Earth's (Venus' mass is 81.5% of Earth's and its volume is 86% of Earth's). Its almost circular orbital period is 224.7 Earth days. A 0.76 albedo makes Venus the brightest planet, earning it the nickname 'the Morning Star'. (The 19th Century astronomer Franz Von Paula Gruithuisen believed that inhabitants on the planet were responsible for lighting objects in celebration of the accession of a new emperor.) Until the early 1960s, Venus was believed to possibly be oceanic even though the temperature was enough to make it a vast desert. Finally, in 1962, the Mariner 2 spacecraft passed by Venus and sent back data putting an end to this hopeful theory.

The atmosphere consists almost entirely (96%) of carbon dioxide (CO₂), a greenhouse gas responsible for the incredibly hot, greater than 400ºC conditions on Venus, surpassing the melting point of lead. The rest of the atmosphere is comprised of 3% nitrogen, 0.003% water vapor, and small quantities of other gases. The atmosphere rises to about 400km above the surface of the planet. The clouds situated around 30 km above the surface are rich in sulfuric acid; during precipitation the acid rain evaporates before hitting the ground. In 1970, the Soviet Union landed the first spacecraft on the planet's surface, Venera 7, which sent back information for 23 minutes before losing contact with ground control (most likely due to the temperature). On October 21, 1975, Venera 9 landed and sent back the first image of the rocky Venusian surface (thereby confirming the high temperatures), returned atmospheric data, and found the rotation period to be 243.2 days, longer than one Venusian year. A Venusian day lasts 118 Earth days, and the Sun rises in the west and sets in the east since Venus rotates in the opposite direction to Earth.

The Magellan probe, carried into space by the NASA shuttle Atlantis on May 4, 1989, and reaching Venus on August 10, 1990, completed radar maps of the planet by September 1992 before gravity-mapping the planet.

Venusian geography is comprised of a huge plain and some highlands and lowlands. The highlands cover approximately 27% of the planet, the lowlands 8%, and the plains the rest. There are two main highland areas known as Ishtar Terra and Aphrodite Terra as well as a third, smaller highland area called Beta Regio where Rhea Mons, Theia Mons, and a shield volcano are found. The highest points on Venus, on the eastern side of the Ishtar Terra, are the Maxwell Mountains that were named after the Scottish physicist James Clerk Maxwell. An edict stating that all geographical names on Venus are to be feminine names in the manner of the planet itself was decreed soon afterward