Does it make sense for the U.S. to expend hundreds of billions of dollars to mount a new Apollo-style program to return to the moon? Or have we blazed that trail? Shouldn't we help other nations achieve this goal with their own resources but with our help?

Climate has been changing for billions of years.

Dwelling on an engine failure for a pilot as he rolls down the runway is NOT what he should be thinking about - it's obtaining a smooth liftoff! But in the back of his mind, he knows exactly what to do (or pretty much) and in many cases, if he's alone in the fighter aircraft, he has to leave that aircraft in an ejection seat in a big hurry!

Space is not just going up and coming back down again. Space is getting into orbit and being there, living there, establishing a presence, a permanence.

Mars is the symbolic and totally stimulating next objective that could so dominate the next century's exploration efforts. From Mars, the resources of all the asteroids will become readily available.

Everyone who's been in space would, I'm sure, welcome the opportunity for a return to the exhilarating experiences there. For me, a flight in a shuttle, though most satisfying, would be anticlimactic after my flight to the moon. Plus, if I pursued a flight myself, people would think that was the reason I am trying to generate interest in public spaceflight. And that's not the purpose - I want to generate interest in long-range space exploration.

I think it's inevitable that there will be Earthlings establishing a presence on Mars. And I would say that it would certainly take place by 2050 or shortly thereafter.