Venus

Venus

**Venus** is the second planet from Sol, orbiting it every 224.7 Earth days. It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets. It has no natural satellite. It is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun; its elongation reaches a maximum of 47.8°.

Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun, and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth. Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 735 K (462 °C; 863 °F), even though Mercury is closer to the Sun. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had water oceans in the past, but these would have vaporized as the temperature rose due to a runaway greenhouse effect. The water has probably photodissociated, and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venus's surface is a dry desertscape interspersed with slab-like rocks and is periodically resurfaced by volcanism.

As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the "morning star" and "evening star". Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC, and was a prime target for early interplanetary exploration as the closest planet to Earth.

## Physical Characteristics

Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass, and is often described as Earth's "sister" or "twin".

About 80% of the Venusian surface is covered by smooth, volcanic plains,
 consisting of 70% plains with wrinkle ridges and 10% smooth or lobate
plains. Two highland "continents"
 make up the rest of its surface area, one lying in the planet's
northern hemisphere and the other just south of the equator. The
northern continent is called Ishtar Terra, after Ishtar the Babylonian goddess of love, and is about the size of Australia. Maxwell Montes,
 the highest mountain on Venus, lies on Ishtar Terra. Its peak is 11 km
above the Venusian average surface elevation. The southern continent is
called Aphrodite Terra, after the Greek
 goddess of love, and is the larger of the two highland regions at
roughly the size of South America. A network of fractures and faults
covers much of this area.