Why Mars? Why Now?

Are we going to go to Mars or not ? Now would be a good time to decide. Are you listening, President Obama? Yes, the president has lots of things on his mind. But that's true of any president, anytime. And the fact is, the U.S. government is already spending billions of dollars a year on a space program that has a trip to Mars as its ultimate but inadequately funded and too-far-off-to-get-excited-about goal.