First, to respond to Mark, I don't think Raoul was saying that getting all our eggs out of one basket was not a valid idea, just that it was not the only, or even the major reason for humans going into space and studying other worlds close up.

We need to find out a LOT more about the universe.

We live on the only known planet that supports life. A science experiment with a single data point. What we learn about how other worlds work, their atmospheres, histories, and maybe even (fingers crossed) ecosystems, will tell us a lot about how Earth works. We didn't get a manual, and we don't know nearly enough yet about things that could be critical.

As you know, I don't think what we know about global warming to date is a good enough reason yet to cripple technological civilization, but I do think that the issue needs intensive study. Temperatures have changed drastically a number of times over the Earth's history, and less drastically a lot more often, and there are as many theories why as there are scientists. What is the sun doing? How many impactors were there through history really? What does the sun do to the atmosphere?

Are we getting more interstellar dust in the Solar System during the sun's 11-year cycle? Does this have an effect on temperature?

It is comforting to know that life on Earth survived hundreds of millions of years of whatever the universe could throw at it, but survival is not the same thing as living in comfort, or thriving. There have been some tough times, and I really would prefer the human race not have to survive those.

And I don't believe we are going to be able to study the universe as much as it needs to be studied using only robot probes. There is not a geologist on Earth that you could convince that he could do just as good a job with a robot and camera substituting for him as he could on site with a hammer and his own eyes. Ask Jack Schmitt.