VENUS

Venus is the second planet from the sun and the sixth largest. Venus' orbit is the most circular of any of the planets, with an eccentricity of less than 1%. Venus orbits 108,200,000 km from the sun. It has a diameter of 12,103.6 km, and a mass of 4.869e24 kg. It has been called Earth's twin, because it is relatively the same size as Earth, both planets have very few craters, and the density and chemical composition of both planets is similar. However, there are many differences. Venus's day is about 243 Earth Days long, slightly longer than Venus's year of 225 Earth days. Due to it's slow rotation, Venus has no magnetic field. Venus' orbit is also retrograde. Venus' atmosphere is made up of mostly carbondioxide. It had thick clouds that cover it, made up of carbondioxide and acidrain. The pressure of Venus' atmosphere is 90 atmospheres. This pressure, along with the carbondioxide in the atmosphere and the thick layer of clouds, create a massive greenhouse effect, raisin the temperature of Venus by 400 K, giving Venus temperatures over 740 Kelvins. Venus has no known satellites.

Venus' surface is mostly rolling plains. There are also several broad depressions, all of which are named after women. Much of Venus' surface is covered by lava flows, which come from volcanoes on the surface such as Sif Mons. Venus is still volcanically active in a few spots, but most of Venus has been geologically quiet. The oldest terrain on Venus seems to be about 800 million years old. Volcanism wiped out the earlier surfaces.

The interior of Venus is probably similar to Earth's, with an iron core about 3000 km in radius, and a molten rocky mantle.

Venus was named after the Roman goddess of love and beauty, probably because it was the brightest planet known in those times. Venus has been known since ancient times because it is the brightest object in the sky, except the sun and moon. At one time, it was thought to be two seperate bodies, the morning star and the evening star.

The first spacecraft to visit Venus was Mariner 2. Since then, Venus has been visited by over 20 spacecraft, the most recent being the spacecraft Magellen, which made detailed maps of the surface.