Venus (2nd rock from the sun) - High in orbit around our nearest sister planet, Venus Express is relaying never before imagined data on the high temperature rock. Venus' atmosphere has 92 times more pressure than Earth. It's comprised of 96.5% CO2 and 3.5% nitrogen. There are molecules of oxygen visible in trace amounts. Its surface temperature is nearly 450C, trailing off to near Earth-like temperatures at an altitude around 60km. Venus also includes high velocity winds in excess of 100 meters per second, and these persist throughout the atmospheric layers to varying degrees.
Each full rotation, or Venus day, is 243 Earth days, and the planet rotates perpendicular to its orbit, resulting in no seasons. The high-temperature surface, coupled with a limited number of impact craters - which would be expected over a long period of time - is theorized to be part of a constant cycle. The planet heats up, heats up some more, and heats up even more, until eventually the surface essentially erupts into a series of volcanoes and molten rock. This results in a new topography which eat away at the impact craters. At the same time, a tremendous amount of heat bleeds off into space from the release. This cools the surface of Venus rather notably. Then, in several hundred thousand years, it cycles again.
There are some amazing images and video sequences of Venus and its atmosphere at the link below. I forewarn anyone visiting that site that it will quickly consume an hour or more of your time.
Read more ... European Space Agency Venus Express.