Remember how important liquid water is to life? Well, if a planet is in the "Goldilocks" zone, it's not too close, and not too far from its star--it's just right. And it's possible for water to flow there as a liquid.We obviously sit in the "Goldilocks" zone, but in our solar system Mars and Venus also do, but we've yet to find life on either those two planets.

 

"Kowning if a planet is inhabitable, is not as straightforward as saying, oh, we found a planet the size of the earth, and it's 90 million miles from a sun-like star. Venus are inhabitable, and Mars are inhabitable."

 

"Why is Venus such a harsh hideous environment? Some 6,00 degrees celsius or so. And of course, the answer for Venus sadly is that some greenhouse effect, global warming, has overtaken Venus."

 

When it formed over four billion years ago, Venus had water, and probably vast oceans on its surface. But there was also a lot of the greenhouse gas water vapor in the atmosphere, which blanked it and heated the planet. And this Venus got hotter. More and more water on its surface evaporated into the atmosphere, trapping the heat even more. 

 

On earth, much of the green gas carbon dioxide is chemically bound to the rocks, and it was this way on young Venus too. But when it've come to about 750 degrees fahrenheit, this carbon dioxide started getting out of the rocks and into the atmosphere. With an atomsphere of water vapour and carbon dioxide, this cycle kept going and going and the runaway greenhouse effect has left Venus dry, lifeless,and...