Dear PF Forum, I would like to know if LIFE in exoplanet is possible. And if it is, how? When I drove my Pastor to my mother funeral, he asked me out of the blue while I was driving my car. "Do you believe there is another earth?" My immediate response would be, in parallel universe where there are Nicole Kidman, Megan Fox, Linday Lohan OR in this universe. "In this universe," he said. So there were the following problems I think. First, life should be in a planet or moon (as in Avatar). This planet must be supported by a nearby star. And for this star: I think the star cannot be too massive. I read that the comparisson between the mass of the star and its lifespan in main sequence is to the power of 3. For example, a 2 solar mass star will have 1/8 lifespan of our sun. 10 solar mass star will have 1/1000 lifespan of the sun. That is: 10 million years. Earth develop life form in 3.9 billion years. "Only" in 600 million years ago (Cambrium) there were many multilcellular organism blooming in the ocean. Trilobite, nautilus, etc... And it takes 4.5 billion years for earth to develop intelligence. And the star cannot be too light, because if it's too cold, then the planet should be closer to the sun, then there are tidal lock problem, and radiaton. So how is the chance for this universe to have, IMHO, stars that are 0.8 - 1.2 solar mass? For these stars to have planet in their habitable zone? I'm not trying to bring Drake Equation, just want to lay out the facts. And after all those... What would that lifeform be? Will it be carbon compound? Since carbon has 4 valence and Carbon is abundance in the universe. I don't know if this number represents carbon in outer space nebulae, or locked in white dwarf stars. Silicon and Germanium have 4 valence, too. But since they are more complex than carbon, I think carbon is easier to build element compound rather than Si/Ge. And Carbon is more abundance than Si/Ge. And IF the lifeform in exoplanet is carbon based, would they develop DNA as their method to replicate? So my summary questions are these: 1. Given those conditions, would extra terrestrial life be possible? 2. IF it is possible, would it be carbon based? 3. IF it is carbon based, would it develop DNA as their replication method? Thank you very much.