Tom Brosz said:

"On the other hand, if you want to colonize Mars someday, when the technology is up to it, getting the supplies there won't be a showstopper. Imagine what Captain James Cook would have thought of today's Honolulu, a modern city which, essentially, had to be brought over by boat."

Assume you start the colony with a 1000 people (a bit more than the minimum number to protect against in-breeding). Assume the population doubles ever 20 years. How long does it take the population to get bigger than 100,000,000? Answer: About 2 and a half centuries. In about the same time it took America to develop from the colonies in Jamestown and Newfoundland into a global super power, a Martian colony could develop into a Solar System wide super power.

Here's the really neat part: Every American is descendant from an immigrant (even the Indians were ancient immigrants although that's nitpicking). This immigrant past represents a major part of America's cultural strength. With a Martian society, every Martian will be a descendant from an interplanetary astronaut. If a 21st century American talks about interstellar travel during a dinner party, he'll be regarded as an educated eccentric. A 25th century Martian won't be talking about it, he'll be building the industrial infrastructure and actively planning the capability. For a 25th century Martian, going to the stars makes as much sense as going to California to a 1849 New Yorker. This is the key to the long term survival of our civilization.

Closing comment: What's the oldest living thing on the Earth? If you answered "redwood tree" or "bristlecone pine" then your answer is incorrect. The oldest living thing on the Earth is human civilization. Human civilization is theoretically immortal provided it can survive beyond its planet of origin.

Gary