Sorry to blow your bubble Mark, but Zubrin's theory that Martian microbes have already innoculated Earth life and therefore pose no risk do not hold any scientific merit and in my opinion are misleading for two reasons:

Number 1: You can still contract diseases from other parts of the world (Earth) even though these germs have shared our planet with us for millions of years. So why would Martian grerms (if any) be any less harmful than our own? You cannot prove they would be harmless, otherwise the National Research Council would not have issued it's most recent report stating that an appropriate Martian Quarantine Facility would take ten years to build. Also, if Zubrin's idea of a shared Earth/Mars biosphere was correct, why is there a planetary protection program etc.?

Number 2: Zubrin says Martian microbes are here on Earth already? Not possible for two reasons: The extraterrestrial material that is infalling on the Earth from Mars was ejected by impact and left Mars hundreds to thousands of millions of years ago. Most of it is not in the form of rocks but rather dust which is incinerated in the atmosphere on contact just as any other meteor dust debris is. True some larger meteorites (rocks) do fall to Earth and are collected. However, Dr. Curt Melikowsky et al have put an upper limit on the survivability of microbial spores inside rocks residing in the galactic radiation and vacuum of space - about 100,000 years.

After that any spores would not be viable, they conclude. Since we know Mars has not suffered any recent impacts (large fresh craters a hundred thousand years or younger), it is doubtful whether any Martian microbes are reaching the Earth alive today. However, if an asteroid were to stirke Mars tommorow and luanch debris into Earth's orbital plane - we might then have some Martian biota survive the trip and something to be very concerned about.

http://www.spacedaily.com/news/life-01r.html

Since we are discussing honesty here, can you tell me this: if the Mars Society is a non-profit organization, why does Bob Zubrin sell his books in every room of a Mars Society Convention? Are the profits from the sales of his books going straight to the Mars Society or his bank account?

BarryD