What Makes a Planet Habitable: The geological history of Earth and the history of life on Earth are intricately intertwined. Earth would be a very different place today if life had not evolved on Earth, and at the same time geological events have greatly affected the course that evolution has taken on Earth.

Considering these statements, how likely is it that that astronomers will eventually discover life on other planets? In other words, what requirements were needed for life to originate on Earth? How likely is it that other planetary objects in the universe also meet these requirements? Consider also a related question: how likely is that a planet will be found that is capable of supporting life, but does not have any living organisms present?

(cite any outside sources)