Keith,

Any errors Zubrin makes with regard to PP pale in comparison to DiGregorio's. Oversimplification pales in comparison to outright misinformation and total lack of understanding of key arguments of debate. When NASA's PP officer makes silly comments like the dutch elm one in response to coevolution arguments anyone capable of logical thought ought to be able to spot the flaw in his argument.

As the one source I thought was most balanced mentioned, the NRC report actually agrees closely with Zubrin with regard to level of threat although not with regard to appropriate precautions. Your examples of potential threat actually seems to side step the NRC's conclusion that Martian organisms are most likely autotrophs. The examples you mention as possible threats outside of Zubrin's frame of reference do not sound like autotrophs to me.

The threat I think is the most likely of a host of low probability ones is the production of toxic byproducts. This is related to some of the threats you mention.

The ecological upset risk is not plausible to me based on examples of known extremophiles. The traits needed to survive in extreme environments (extreme simplicity or suped up molecular biology) place them at a competitive disadvantage where such traits are not needed. The idea that "superpowers" make extremophiles supercompetitive is simply wrong. If it were correct these would be the normal form of life on Earth not the "weird" ones.

That said, I do wish Zubrin would shut up and delegate the debate to someone more qualified, because his comments come across as inflammatory and often as closed minded as DiGregorio's. His knowlege of biology also seems to be too limited to deal with many of the issues you and others have raised with regard to potential risks. I am probably more qualified than Zubrin based on training alone (although possibly not based on subsequent professional interaction and reading), and I would prefer a public voice of reason with much more expertise than me to counter DiGregorio.

I certainly would hope someone with far more expertise would act as a public champion against excess caution within the planetary science community. Someone needs to take such a stance to counter the natural overcautious reaction to people such as BD.

Regards,
Mark

PS a rational discussion of PP issues is a most welcome change.