RE: 1) There are no hostile organisms on Mars.

There are known hostile organisms on Earth. MY GOD, WE'VE GOT TO GET OFF THIS PLANET and colonize one without such organisms. Obviously a hysterical over reaction. Hostile organisms can be delt with effectively and we have plenty of procedures for that which we should be able to modify for use on Mars if needed.

At any rate biological experts have rated the odds that Martian life would be hazardous as almost 0. Simple scientific precaution is the basis for recommending treating Martian samples as hazardous until proven otherwise.

2) People can thrive in 1/3 Earth gravity for long periods of time.

Obviously a major assumption for colonization. It is one reason I do not support one way mission plans. 0 g experience suggests but does not prove than astronauts should be able to endure reduced g for the mission times planned. The Mars Society is planning on addressing this issue through it's 50 day translife mission which will simulate Martian gravity in LEO with a group of mice to compare the effects with 0 g and on reproduction.

3) A way (or ways) can be found to counter the severe radiation which bathes the surface of Mars.

They're called sandbags. This high tech solution has been brought up before, but you seem unfamiliar with the term.

I have to concede that we may have already missed our window of opportunity if we allow terrorists to have more and more control over our expenditures and loose the relative global stability we had just a few years ago. Such worries are why I think colonizing space is an ASAP priority not something to be done after a long checklist of baby steps as some here have proposed. Incrementalism has a large opportunity and dollar cost.

Regards,
Mark