Or, as many on this Board like to quote: Mars is Mars

Think about how the Polynesians colonized Hawaii and New Zealand. They didn't do it with hundreds of thousands of people travelling in Boeing 747s. They did it with hundreds of people in open outrigger canoes voyaging thousands of miles across open ocean with almost no navigation.

True -- but:

They traveled in steps from island to island, through a breathable atmosphere that shielded them from the most harmful radiation (their melanin helped reduce the effects of UV-B, and the geomagnetosphere helps, too...). They were able to replenish supplies en route, as well.

Any Polynesians among the regulars (or even the lurkers) here? Anyone living in Hawaii, NZ, or elsewhere in the Pacific? [Alex, how's your non-haoli history?] What, if anything, is known about the success rate of Polyensian migration; that is, how many failed attempts, and brave people lost, were there as a percentage of the successful colonists?

Raw numbers of people don't make anything like a true comparison between colonization attempts. It's like apples and coconuts...

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"Lifeboat Mars" gives me the creeps.

As a collateral benefit of just happening to have humans on Mars if the Big Rock hits Earth... sure, OK. But if the "lifeboat" concept catches on as a motive to colonize Mars, it opens up a huge can of nasty worms. Who gets to go, and why? Which nations, cultures, linguistic groups, religions, etc., don't - and why? Do we transfer unique cultural assets? Which ones? What other, non-human, Earth life?

It's Ray Bradbury's The Shelter, writ very large... and there's plenty of other examples in our favorite speculative literature, too (including, lame though it is, When Worlds Collide).

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I wonder what the comparative probabilities are of any class of large rock (or dirty snowball) hitting either planet - taking into account such things as Mars' weaker gravity and smaller cross-section vs its closer proximity to the sources of impactors, and to the Big Perturber of orbits, Jupiter...

E' (just thinking out loud)