What Happened to ... The Observer Updated

For the past two years, Venus Express - a spacecraft built by European scientists and engineers - has been orbiting the Earth's sister planet. This week, astronomers will gather in Paris to reveal what the probe has told them about this strange world.

Despite the powerful solar radiation that has battered Venus Express, the craft has operated flawlessly since its launch in November 2005.

Scientists already knew Venus was a strange world, afflicted with a crushing dense atmosphere, surface temperatures that would melt lead and clouds laced with sulphuric acid. And the surprises have continued to emerge from the data sent back the European Space Agency's spacecraft. In particular, researchers have found that Venus's atmosphere is extremely fickle and changes its structure from day to day.

Images sent back by Venus Express show that, at both poles, there is a giant double-vortex, each 2000 km across, similar to the eye of a hurricane. The double-vortices rotate in opposite directions - clockwise at the north pole, anti-clockwise at the south. Venus Express has also found the southern vortex changes its shape rapidly.

In addition, astronomers have found that the planet emits a glow of infra-red radiation, which has been used to make maps of the Venusian surface and to pinpoint its mineralogical composition.