Mars has been flown by, orbited, smacked into, radar examined, and rocketed onto, as well as bounced upon, rolled over, shoveled, drilled into, baked and even blasted. Still to come: Mars being stepped on.

To send humans back to the moon would not be advancing. It would be more than 50 years after the first moon landing when we got there, and we'd probably be welcomed by the Chinese. But we should return to the moon without astronauts and build, with robots, an international lunar base, so that we know how to build a base on Mars robotically.

Mars, we know, was once wet and warm. Was it home to life? And what can living and learning to work on its rust-colored surface teach us about the future of our own planet, Earth? Answering those mysteries may hold the key to our future.

There were about six years when there was not one American who went into space. We shouldn't do that again.

Mars is far more attractive as an outpost colony for earthlings than the moon is.

Training was very extensive, and we dealt with many recoveries from emergencies, and fortunately, participating and observing and existing through the reality of space was a once-in-a-lifetime experience and it was not marred by unexpected hazards or catastrophes.

It's time to open the space frontier to citizen explorers.