Venus, named for the roman goddess of love, is often referred to as Earth's Twin or Earth's Sister. But, Venus does not bare much of a visual resemblance to Earth, so why is it called Earth's sister?
From a strictly physical perspective Venus is roughly the same size, density and composition as our planet. It orbits at a similar distance from our Sun, and at its creation would have appeared nearly indistinguishable from Earth. As the two planets evolved over time however, they became vastly different. Ultimately, Earth's sister was molded into a desolate and unforgiving world.
At nearly 108,209,000 kilometers, Venus is the second planet from the Sun, and is Earth's nearest neighbor (besides our Moon). In fact, Venus is so close, and so bright (due to the Sun's reflection off its atmosphere), that it is the only object besides our Moon that can be seen from Earth during the evening and during the day!
Venus takes 225 Earth days to complete one orbit of the Sun. And like the other planets in our solar system, Venus rotates about its axis. However, Venus is the only planet that rotates from east to west instead of west to east. This means, that if we lived on Venus, the Sun would appear to rise in the west in the morning, and set in the east in the evening! Even stranger, Venus rotates so slowly that one day on Venus is equivalent to 117 days on Earth.
At approximately 4.9 x 1024 kilograms, Venus is also nearly as massive as Earth. As a result, the gravity on Venus (8.87 m/s2) is nearly the same as it is on Earth (9.81 m/s2). Additionally, scientists conclude that the structure of the planet's interior is similar to Earth's, with an iron core and a rocky mantel.
The Venusian Surface
Venus is one of the terrestrial planets -- those with solid, rocky surfaces inhabiting the inner part of our solar system.
The surface of Venus is a very desolate, barren place. Nonetheless, efforts were made to study the planet by several Soviet Venera spacecraft. These spacecraft were able to take pictures, as well as sample rocks and take other various measurements.
The rocky surface of Venus appears to have been created through volcanic activity, and is comprised of low, rolling plains. While the highest elevations of Venus rival those of Earth, these features are less abundant. In fact, the elevated areas, similar to continents here on Earth, only comprise about 8% of the total surface area, compared to 25% of the surface area on Earth.
There is also a lack of small impact craters, like those seen on the other terrestrial planets. This is due to the thickness of the Venusian atmosphere which prevents all but the largest meteors from reaching the surface.
The Venusian Atmosphere
By now you may be asking yourself "what's the catch?" After all, you have undoubtedly heard about NASA's plan to send a man to Mars, and how someday we could actually create a colony on that planet. What about Venus? It is closer to us than Mars, more similar in size, and has similar gravity!
The answer to this question lies in Venus' atmosphere. The Venusian atmosphere is very different than the atmosphere on Earth, and would have devastating effects on humans if we attempted to live there.
The Venusian atmosphere consists mainly of carbon dioxide (~96.5%), while only containing about 3.5% nitrogen. This is in stark contrast to the Earths atmosphere, which contains primarily nitrogen (78%) and oxygen (21%). Clearly, we would not be able to breath the air on Venus. Moreover, the effect the atmosphere has on the rest of the planet is dramatic.
Global Warming on Venus
A great cause for concern on Earth is global warming, specifically the emission of "greenhouse gases" into our atmosphere. As these gases accumulate in our atmosphere, they trap heat near the surface, causing our planet to heat up. Because Venus has such a dense atmosphere, this same effect has occurred, though to a much higher degree. Global warming on Venus has caused the surface temperature to rise to nearly 9000 F, enough to melt lead.
Living Conditions on Venus
As destructive as the surface temperature of Venus is, just as troubling is the immense pressure you would feel standing on the surface. The weight of the atmosphere is 90 times greater than that on earth -- the same pressure we would feel if submerged under 3,000 feet of water. This pressure is so high, that when the Venera spacecrafts landed, they only had a few moments to take data before they were crushed and melted. Ultimately, Venus appears as a visual beauty in the night sky, but it will have to be admired form afar. As the heat and pressure that characterize the surface of the planet make it unfit for life.