Guest: Alan Boss, Ph.D.

NASA's Kepler mission is the first space telescope designed specifically to look for planets similar to Earth outside of our solar system. In his recent book The Crowded Universe, astronomer Alan Boss argues that Earth-sized planets are plentiful in the universe. He joins the show today to talk more about the formation of Earthlike planets and the search for extraterrestrial life.

Guest: Steven Squyres, Professor of Astronomy at Cornell University.

Twin robotic explorers Spirit and Opportunity have added a great deal to our understanding of Mars. Among other things, they have found substantial evidence that at one time, there was water on the surface of the planet. Today on Focus, Cornell University astronomer Steven Squyres talks us through what we know so far and the big question... was there ever life on the Red Planet?

Guest: David Grinspoon.

Where do planetary science and philosophy intersect? In one fascinating field: the search for extraterrestrial life. Today on Focus, David Grinspoon speculates about the possibility of life on other planets and in other solar systems, how intelligent life may evolve both on our own planet and in the rest of the universe, and what the philosophical implications of these future discoveries may be.