Read Professor Kane's post here: http://www.civilization.com/en/news/2014-11-the-dr-jekyll-and-mr-hyde-of-planets/
In addition to this post, Professor Kane also discussed the plurality of worlds - the abundance of planetary types that are likely out there in the cold reaches of space. Before mankind finds a new home, we'd likely have to sift through a daunting array of inhabitable planetary bodies.
Another post from Professor Kane, entitled Discovering the New Beginning , talks about how the past two decades have provided scientists with exciting new exoplanetary data that has progressed our ability to discover and catalog new exoplanets. It's this data that has excited scientists and lended more creedence to the possibility of life beyond Earth.
I hope you enjoy Professor Kane's posts and I'll be sure to let you all know about any future posts the professor is kind enough to share with us.