Introduction
© Andrzej Mirecki
Venus and Earth are almost equal in mass and radius and appear to have evolved from very similar beginnings, yet the surface climate on both planets is very different. However, first results from the Venus Express mission that reached the planet in April 2006 suggest that despite their dissimilar surface temperatures, Earth and Venus have a lot in common.
Håkan Svedhem at the European Space Agency, Nordwijk, Netherlands, and his colleagues1 give an overview of a suite of papers analysing the data from the first year of the Venus Express mission that launched from Kazakhstan in November 2005. They report that, like Earth, Venus has a longitudinal atmospheric overturning circulation — the Hadley circulation. Because of the planet's slow rotation, the Venusian overturning extends substantially further poleward than on Earth, to 
60° of latitude, where it transits abruptly into the polar circulation — a vortex-type structure with a double eye.
In addition, the mission revealed a lightning rate on Venus that is about half of that on Earth, constituting a substantial energy input into the lower atmosphere, with potential implications for atmospheric chemistry.
