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Venus Express : Venus, world of mysteries
ESA, le 20/08/05

You cannot understand the Venusian weather and atmosphere by comparing them to Earth's. Scientists are unable to explain some of the more extreme atmospheric phenomena that take place on Venus. For example, the planet only rotates once every 243 Earth days. However, in the upper atmosphere, hurricane-force winds sweep around Venus, taking just 4 Earth days to circumnavigate the planet.

The surface of Venus also baffles scientists. The oldest craters seem to be only 500 million years old, which may indicate that the planet behaves like a volcanic pressure cooker. On Earth, the constant, steady eruption of volcanoes and the shifting of the Earth's surface, causing earthquakes, ensures that the energy released in the Earth is dissipated gradually.

This probably does not happen on Venus. Instead, pressure builds up inside the planet until the whole world is engulfed in a global eruption, resurfacing the planet and destroying any craters that have formed. This probably happened last, 500 million years ago and so accounts for the lack of older craters. Today, there is a strong relationship between the surface and the atmosphere. Is there any similarity between the ocean-atmosphere relationship on Earth and the surface-atmosphere relationship on Venus? Venus Express will supply scientific data that could shed light on both of these mysteries.

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