Mars is a long ways away. The moon is only 240,000 miles, but Mars is in the millions. It's too risky without spending more time going to the moon.

In space-flight terms, six landings on the moon back in the Sixties and Seventies doesn't mean much.

I was a naval officer and aviator. I tested airplanes and got selected to be an astronaut later on.

People say, 'Did you violate Heaven?' Well, God is down here, too. If you believe in God, you believe in God here as well as 240,000 miles away.

After six successful Apollo flights, including two lunar landings, people were getting bored.

I was born a year after Lindbergh made his historic trip across the Atlantic.

My view is that we should go back to the moon, build up the infrastructure to make flights there commonplace - be comfortable with it - then use that infrastructure to expand and go to Mars.

I take the NASA physical every year.

We got to the moon on Christmas Eve 1968, at the end of a poor year for this country. We had Vietnam. We had civil unrest. We had the assassinations of Robert Kennedy and Martin Luther King. But we went around the moon and saw the far side for the first time. A script writer couldn't have done a better job of raising people's hope.

For some time, I thought Apollo 13 was a failure. I was disappointed I didn't get to land on the moon. But actually, it turned out to be the best thing that could have happened.