Then how do you explain the dead unicorns?

Science found evidence of carbon dioxide on a planet outside our Solar System. The New York Times has this to say:

"The planet, HD 189733b, is far too large (about the mass of Jupiter) and too hot (1,700 degrees Fahrenheit) for any possibility of life."

Why do scientists get stuck on the idea that life can thrive only in the narrow set of conditions existing on Earth? With preconceptions like that, they could look right at life and not see it. It's poor science to define what you're looking for before you find it.