Is there life on planets in other solar systems?

Because of great distances, it has been impossible for scientists to determine whether or not planets in other solar systems contain life. If we were able to gather data about the extrasolar planets, we might be able to tell if there is life on another planet. In particular, the presence of carbon dioxide could tell us that the planets have an atmosphere; a significant amount of water vaporwhich is unique to Earth's atmosphere in our solar systemwould tell us that a planet has an ocean; and ozone, the layer of gas that protects life on Earth from the ultraviolet radiation from the Sun, may tell us if a planet has life.