Macintosh: We can't go back in time and study what conditions were like on the Earth four billion years ago to understand how life evolved. But we can look at planets like Titan. All the other planets have no atmosphere like Mars, or thick, crushing atmospheres like Venus. Titan is the only place that has an atmosphere that's roughly like the Earth's - that's mostly nitrogen.
Narrator: Macintosh says such scientific knowledge has broad implications.
Macintosh: Understanding things like the origin of life at least gives us a feeling for our place in the Universe for whether life is something that's very rare and unique to the Earth. Or whether life is something that occurs relatively commonly and could occur in many other places throughout the Universe.
Narrator: For Science Today, I'm Larissa Branin.