Let's see Zubrin is ungualified to speak on this issue because he does not have a relevant degree in microbiology, but Benton Clark is the final word because he doesn't either? Strange how only those that agree with you like Sanitation Engineer Gil Levin are qualified to debate issues outside their primary field of expertise, but not those that disagree with you. More of that superb scientific background of yours showing through Barry. Since Clark is not a microbiologist and all the accomplishments you mention indicate no expertise on biohazards or meteorite mediated transfer I am not at all intimidated by his opinions. You as usual appear afraid to tackle these issues using your own words and logic.

I'd also like to point out that I support NASA's original planetary protection plans and the recommendations of the Mars Sample Return Issues and Recommendations report contrary to your claims. While it may be that Zubrin may considers some of these recommendations overkill that is a valid point of arguement given the issues he raises. What I constantly call you to task on is your self contradiction with regard to panspermia - embracing it when it suits you, denying it when it contradicts you. I do not necessarily agree with Zubrin on what constitutes acceptable risk.

It is also strange that you fail to address the comments I have made on many of Benton's points directly. I would like to point out that Benton Clark was not on the Mars Sample Return: Issues and Recommendations Report Team as Nealson and Race were. Why don't you address my comments directed at these seemingly more knowledgible experts?

As for Benton Clark's points, I'd like to point out that you only listed an abstract. You have misleadingly done that in the past with B. CLark articles. For what its worth, here are my comments:

RE: "The phenomenon of natural transport of material from the surface of Mars to the surface of planet Earth, in the form of martian meteorites, cannot be used as justification to relax or abolish plans and procedures for quarantine and strict sample containment for future Mars sample return missions (MSR)"

Agreed. Zubrin agrees as well at least in part: "Everyone agrees that measures should be taken to preserve the scientific value of the Mars sample. " from Robert Zubrin Responds The big issue is that neither Clark or Zubrin are the ones best qualified to judge what protective measures are adequate. Both might have valuable insite on mechanical containment measures, but neither can as accurately assess the hazard as microbiologists and medical doctors.

RE: "Biosphere upsets, ecological disasters, and species extinctions have been far too numerous and their causes too poorly understood to rule out occasional possible contributions from exogenous biological invaders."

This was dealt with earlier. There is no accepted evidence of diseases from space. There is even little evidence for extinction on a species scale by any disease without combination with other important factors like limited range or concurrent stress from other factors. The fact that there are many well known causes for mass extinctions and species extinctions leaves no rational basis for this claim. It is scientific speculation and nothing more. While possible, the Mars Sample Return: Issues and Recommendations Report makes it quite clear why this is unlikely. The mere possibility however, warrants taking precautions as the report recommends in my opinion.

It appears on the basis of the abstract that Benton Clark is not familiar enough with this report or microbiology to understand this information. I truly doubt this as I have read some of his work and find it very broad and in depth. I think it is more likely that you are quoting a short abstract to obfuscate comments more contrary to your point of view as you have in the past with both Clark and Sagan.

On the other hand if you believe Martian meteorites have caused catastrophe in the past despite a total lack of evidence then a rational person would want to study the threat under controlled conditions to develope methods of mitigation just as we do for all other known pathogens.

Overall Clark's abstract doesn't explicitly recommend anything different from the report linked above. He just plays up the potential negatives without indicating at all how truly low probability they are. On the basis of the abstract alone it is not at all clear whether he has the knowledge to judge the relative risk associated with these potential negatives.

Regards,
Mark