Most here are well aware of the catastrophic potential of asteroid impacts, but there is another seldom mentioned which occurs on a similar timescale and for which we have no forseable technological solution. John Young' comments mention super-volcanoes, but little info is provided. A recent article on Yellowstone's catastrophic potential can be found at http://www.spacedaily.com/news/tectonics-02h.html . Yellowstone is not the only potential supervolcanoe site either. The Discovery Channel or TLC has shown some documentaries on this hazard. Getting our eggs out of one basket will help develope the technology to prevent impacts and will prevent our extinction or civilization' collapse in the event of extinction level impactors or supervolcanoes.

Noticiably missing was a list of any reasons why returning to the Moon is needed prior to going to Mars. One reason so many NASA people may be interested is it provides job security by greatly increasing the time and cost needed to reach Mars, or more likely it is simply the slow and steady low risk approach. While there is no doubt we can use lessons and technology from returning to the Moon to get to Mars it doesn't seem to me we need the Moon to learn these lessons. For Instance some research needed for colonization & exploration of Mars:

Long term effects and mitigation of 0 g. ISS sufficient no need for the Moon

Effects and mitigation of radiation. I think can be simulated on Earth using radioactive materials and/or particle acelerators. Anyone know for certain?

Long term effects on health and reproduction of 0.38 g. Moon and ISS too low. LEO centrifugal simulation or robotic Mars missions needed. Moon could set lower limit but why not go for a closer simulation?

Mars suits. similar to above.

Heavy lift launch vehicles. I think they should be developed for Mars and tested with a few manned missions to the Moon with obvious scientific or commercial value such as looking for resources valuable for the commercial use of the Moon or setting up some robotic research stations.

The huge impact on taxpayer expense seems of little concern and certainly is not mentioned.

It also seems to me that once NASA completes the ISS finishes exploring Mars and there are few long other term research goals it can look toward requiring human spaceflight. If that is the mindset, I think it is short sighted because I think we will find plenty of questions to motivate extended research programs on Mars. It has already been proven that the Moon can not sustain long term public interest so basing plans on an extended phase there is a risky path in terms of actually reaching the final goal of Mars. We will end up in a situation like the ISS where the final phase is cut because the intial phase has cost so much and garnered little public interest.

I'm all in favor of a human presence on the Moon, but I think it should be commercially viable. With a commercial infrastructure in place NASA would find building reseach facilities and telescopes there far cheaper. Mars makes a better target for colonization, but the Moon is a far likelier tourist target. In that field its closeness does make it far supperior to Mars. I think Mars, would be more interesting, but few could commit the time required let alone the money to reach it even with far cheaper launch vehicles.

Regards,
Mark