Venus is the second planet from the Sun and the sixth largest. Venus' orbit is the most nearly circular of that of any planet, with an eccentricity of less than 1%.

orbit: 108,200,000 km (0.72 AU) from Sun

diameter: 12,103.6 km

mass: 4.869e24 kg

Venus: The brigthest object known by the ancients, the "morning star" and "evening star", is the second planet closer to the Sun. Is similar to the Earth: Both have atmosphere, their dimensions are similar, and also their densities and chemical compositions (sometimes, the planet is considered the Earth's twin sister). Because of these similarities, it was thought that below its dense clouds Venus might be very Earthlike and might even have life. But, unfortunately, more detailed study of Venus reveals that in many important ways it is radically different from Earth.

The first spacecraft to visit Venus was Mariner 2 in 1962. It was subsequently visited by many others, including Pioneer Venus and the Soviet Venera 7 (the first spacecraft to land on another planet), and Venera 9 which returned the first photographs of the surface.

Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde. In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach.

The pressure of Venus' atmosphere at the surface is 90 atmospheres, composed mostly of carbon dioxide, producing a run-away greenhouse effect that raises Venus' surface temperature by about 400 degrees to over 740 K (hot enough to melt lead). Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the Sun. There are strong (350 kph) winds at the cloud tops but winds at the surface are very slow, no more than a few kilometers per hour.

The interior of Venus is probably very similar to that of Earth: an iron core about 3000 km in radius, a molten rocky mantle comprising the majority of the planet. The planet has no magnetic field, perhaps because of its slow rotation. Also has no satellites, and thereby hangs a tale. The planet is usually visible with the unaided eye.