Is life on Earth special? Not according to Carnegie Institution's astronomer Alan Boss. The author of the new book The Crowded Universe: The Search for Living Planets predicted that there may be 100 billion Earth-like planets in the Milky Way:
[Boss] made the prediction based on the number of "super-Earths" -- planets several times the mass of the Earth, but smaller than gas giants like Jupiter -- discovered so far circling stars outside the solar system.
Boss said that if any of the billions of Earth-like worlds he believes exist in the Milky Way have liquid water, they are likely to be home to some type of life.
"Now that's not saying that they're all going to be crawling with intelligent human beings or even dinosaurs," he said.
"But I would suspect that the great majority of them at least will have some sort of primitive life, like bacteria or some of the multicellular creatures that populated our Earth for the first 3 billion years of its existence."