1. We know that evolution of life requires a degree of stability for long periods of time, and most likely conditions favorable to having a liquid solvent for chemical reactions to occur (probably water but possibly things like methane). Those conditions are relatively rare, which is why scientists talk about the "habitable zone" of planets around stars.
2. Given the requirements of a habitable zone and long periods of environmental stability, that knocks out pretty much the entire rest of our solar system, with the possible exception of some of the gas giant moons.
3. It hasn't really been proven that life is not abundant in the universe. There is a really good section in How the Mind Works that talks about some faulty assumptions in the Drake Equation (primarily that evolution "drives" towards more complex, intelligent life forms over time), but AFAIK we haven't ruled out the possibility of life in many of the planetary systems we've discovered. On the contrary, we've recently discovered many extra solar planets in the habitable zone of their stars, with signatures of water.
1. We know that evolution of life requires a degree of stability for long periods of time, and most likely conditions favorable to having a liquid solvent for chemical reactions to occur (probably water but possibly things like methane). Those conditions are relatively rare, which is why scientists talk about the "habitable zone" of planets around stars.
2. Given the requirements of a habitable zone and long periods of environmental stability, that knocks out pretty much the entire rest of our solar system, with the possible exception of some of the gas giant moons.
3. It hasn't really been proven that life is not abundant in the universe. There is a really good section in How the Mind Works that talks about some faulty assumptions in the Drake Equation (primarily that evolution "drives" towards more complex, intelligent life forms over time), but AFAIK we haven't ruled out the possibility of life in many of the planetary systems we've discovered. On the contrary, we've recently discovered many extra solar planets in the habitable zone of their stars, with signatures of water.