James Green, director of planetary science at NASA, talks about the places in our solar system that could have alien life in a speech presented at an official TED conference. He explains that as Carl Sagan always said, “It takes extraordinary evidence for extraordinary claims,” the claims of having life beyond Earth must be clearly defined and well formulated, they need to be loud and they need to be everywhere for us to be able to believe it.

So, after carefully examining all the possibilities and also the ingredients of life such as liquid water, energy, and the presence of organic material in certain places beyond earth, James says these four places – the planet Mars and three moons of the outer planets: Titan, Europa and small Enceladus – could have alien life.