Planet Venus: Earth`s "evil twin"
The Babylonians called it "Ishtar". To the Mayans, it was known as "Chak ek", which translates as "great star".
Some ancient astronomers believed it was two separate objects: a "morning star" and an "evening star".
Venus is the brightest object in the sky except for the Sun and Moon. As such, the second planet from the Sun has fascinated humankind for millennia.
Europe`s Venus Express spacecraft blasts off this week, and will rendezvous with our nearest planetary neighbour next year to study it from orbit.
The mission aims to shed light on an enduring mystery about this world: how a planet so similar to our own in size, mass, and composition has evolved so differently over the last 4.6 billion years.
Venus has undergone runaway greenhouse warming, whereby trapped solar radiation has heated the planet`s surface to an average temperature of 467C (872F) - hot enough to melt lead.
A dense atmosphere, composed chiefly of carbon dioxide (CO2), generates a surface pressure 90 times greater than that on Earth.
Exotic vision
Through Venus Express, scientists hope to understand better the mechanics of climate change on our own planet.
"Earth can certainly take a very uncomfortable step towards Venus, though it`s not likely to go all the way," comments Fred Taylor, Halley Professor of Physics at the University of Oxford, UK.
"The point is, we`re moving in that direction and many of the constituents and mechanisms involved are the same. Even a few degrees change in temperature can be a disaster on Earth."
And studying our neighbour could help verify computer models to predict how climate change will affect Earth. "Venus provides an extreme test for the atmospheric physics models that we have for Earth," says Andrew Coates of the Mullard Space Science Laboratory at University College London, UK.
The prevailing view of Venus used to be very different. "Even though Venus is closer to the Sun, its cloud cover is very shiny and reflective," Fred Taylor explains.
"If you work out the energy balance, Venus is actually absorbing less heat from the Sun than the Earth is. By-and-large, you might expect surface conditions to be the same."
NASA
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