Venus
Venus is the second planet from the Sun, 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 vaporised 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.[19] Venus's surface is a dry desertscape interspersed with slab-like rocks and 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. It was the first planet beyond Earth visited by
a spacecraft (Mariner 2) in 1962, and the first to be successfully landed on (by Venera 7)
in 1970. Venus's thick clouds render observation of its surface
impossible in visible light, and the first detailed maps did not emerge
until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more complex missions, but they are hindered by Venus's hostile surface conditions.
