It would be impossible in a few words to describe all that we've found with Cassini. No mission has ever gone as deep for as long on a planetary system as rich as Saturn's.

By the time I finished high school, I knew I wanted to become an astronomer. By the time I finished college, I knew I wanted to be part of the American space program. And that's exactly what I did.

I am uneasy about having scientific exploration depend on profit-making companies.

There's nothing in this world like being the first to discover some fundamental fact of nature. It's profoundly satisfying.

Cassini was so profoundly, scientifically successful. It's amazing to me, even, what we were able to do right up until the end.

Whenever we humans think that we might be approaching something that is vaguely similar to Earth, we get very excited about it. The prospect of something familiar but yet so distant and so strange is a very exciting combination.

Saturn itself is a giant planet, and there's much to be gained by investigating its meteorology and studying its magnetic field.

Even if the ocean on Enceladus starts out being as microbially poor as the pelagic ocean on Earth, which is the worst case, we still have a chance of seeing lots of organisms in the plumes.

Scientists tend to come in two stripes: those who have tremendous appetite and aptitude for the details, and those who illuminate the big picture. Sagan was definitely in the latter category, and he was profoundly good at it. He made connections that others did not have the intellectual breadth or courage to make.

'Carl Sagan: A Life,' though a riveting tale, tells as much about the all-too-human feelings of jealousy and resentment as it does about the individual who inspired them.