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.
Venus Express also found lightning on Venus. This makes the 4th planetary body in our solar system to have lightning. The others three are Earth, Jupiter and Saturn. The lightning on Venus comes not from water vapor clouds, but from sulfuric acid clouds. These rain a fairly constant drizzling of sulfuric acid on the surface. Chris Russell at the University of California at Los Angeles, who was part of the magnetometer team that searched for, and found, lightning on Venus, said, "There may be as much lightning on Venus as there is on Earth." Lightning is important because it breaks down molecular chains into fragments which can be joined in unexpected ways.
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.
David Grinspoon, a Venus Express interdisciplinary scientist from the Denver Museum of Nature and Science in Colorado, said, "Venus has suffered a radical climate disaster but we don't yet know how, why and when." He goes on to explain that at some point in the past, Venus had a lot of water. Over time it has been lost. The article reads, "Venus may once have had this much water as well but it has been gradually stripped off into space by the collision of energetic particles from the Sun. Today, Venus Express has shown that the last remnants of the process are still taking place with the escape of hydrogen and oxygen from the top of the atmosphere." The water vapor which remains in Venus' atmosphere, if it could be condensed onto the surface, would be just over 1 inch thick. Compare that to Earth's nearly 2 miles thick.
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.