For years, her beauty was the stuff of dreams. Then, when that beauty was stripped away to reveal horror, she was abandoned.

Now Earth wants to reach out to her once more.

If all goes well, at 0333 GMT on Wednesday, a Russian rocket will blast off from the Baikonur Cosmodrome in Kazakhstan, taking aloft the first dedicated mission to Earth's closest neighbour in more than a decade.

Its payload is the Venus Express, an unmanned European Space Agencyspacecraft that will orbit the planet, scanning it with powerful tools with the goal of understanding its strange, terrifying climate system.

Venus, the second planet from the Sun, is often referred to as our sister.

Like Earth, the third rock from the Sun, it is a solid planet.

The planets are also astonishingly similar in size and density, and they were both formed at about the same time -- some 4.5 billion years ago, from a thickening cluster of orbiting dust and gas.

"There the similarities end," ESA notes bleakly. "Venus has no surface water, a toxic, heavy atmosphere made up almost entirely of carbon dioxide (CO2) with clouds of sulphuric acid, and at the surface the atmospheric pressure is over 90 times that of Earth at sea-level.

"The surface of Venus is the hottest in the Solar System, at a searing 477 Celsius (890 Fahrenheit)."

In short: Temperate Earth is a paradise, a place of riotous biodiversity; Venus is quite literally a hell.

It was not always seen that way.

From the middle of the 17th century, astronomers began to popularise the notion that Venus -- so close, so bright, so warm -- was a haven for life.

A catalyst for this perception was France's Camille Flammarion (1842-1925), whose writings were a huge inspiration for science-fiction novellists of the 1930s and 40s, led by Edgar Rice Burroughs.

Like colonial Africa, Venus was seen as a virgin world with a hot, steamy jungle climate and its inhabitants were exotic, dangerous and sexy -- "Venus Swamp Girl," a lurid story of the time, being a good example.

All this made Venus prime choice for the first interplanetary missions of the space age.

But what a shock it was, in the mid-1960s, when the pioneering Soviet and US probes sent back data showing a scorching landscape with a suffocating and poisonous atmosphere.

With that, interest in Venus quickly petered out, and mission funding switched to the distant gassy giants which form the Solar System's big outer planets and to Mars, fourth planet from the Sun.

The last dedicated mission to Venus, other than a flyby, was by the US probe Magellan, from 1989-94.

It used high-quality radar to make detailed maps of Venus' topography, covering about 98 percent of the surface. The probe revealed canyons, mountains, volcanoes and volcanic formations as well as craters.

But there are no almost no craters that are less than two kilometersmiles) in size. Smaller space rocks probably burned up by friction with the thick atmosphere before they reached the surface.

This time around, the prime focus is not on terrain but on Venus' atmosphere and clouds -- aerosol clusters of great complexity and variety, driven by winds that at some heights are faster than the most powerful terrestrial hurricane while at others, close to the surface, are no stronger than a slight breeze.

These clouds are mainly responsible for Venus' terrible heat, and understanding how they work will shed light on an important aspect of Earth's greenhouse-gas problem.

Venus clouds reflect back 80 percent of the radiation from the Sun. Another 10 percent is absorbed by the clouds themselves, which leaves just 10 percent to filter down to the surface.

But the clouds are such an efficient insulator that the surface heat gets stored up, turning the place into a pressure cooker capable of melting metal.

Of special interest is the mechanism that causes these very distinct zones in wind velocity and of enigmatic clouds in the high atmosphere, visible only in ultraviolet light, that somehow absorb half of the solar heat received by the planet.

Venus Express marks Europe's first exploration of the Evening Star.

The sister to Mars Express, which is in orbit around the Red Planet, carries a payload of seven instruments, ranging from a camera to sensors to measure infrared and ultraviolet light, magnetic fields and space plasma.

After a 162-day hop, the craft is scheduled to arrive off Venus next April, when it will be placed in an elliptical orbit, swooping to as low as 250 kilometres (156 miles) above the surface to a height of 66,000 kmsmiles).

Venus Express, whose total mission costs are 220 million euros (264 million dollars), has enough fuel to operate for 1,000 Earth days, ESA says on its website

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