I'm certainly loath to disagree with Gary on anything unique to aerospace engineering and always appreciate his support out of respect for his intellect, but there are a number of areas I feal quite free to disagree with Gary on. Exobiology and the environment are 2 of them.

Gary and I aren't really very far apart on exobiology in general IMO and I don't claim he is wrong with regard to Mars, I'm just unconvinced by his arguements. I doubt very much SETI will be successful and I think some of the excuses they give for failure to date are rather weak, but beyond a doubt the approach to detecting intelligent life through radio signals is a scientifically valid one. There is nothing wrong with scientifically trying to prove something even if you're chances of succeeding seem to be decreasing with additional data. As noted below I don't think much of the Drake equation'a ability to predict anything even if almost every term in it were known at the current point in time. However, I don't think any term in the equation is unknowable given more time (possibly centuries or millenia).

If you go through the Sciam articles on the issue you will quite clearly see Lombourg misrepresented the work of others based on their own comments. My sense from reading his comments and having a hard time following the details myself is that Lomborgs mistakes were mostly if not totally honest and that he did not warrant the Danish sanction. He did however warrant the vigorous scientific rebuttal he received. Some other comments on Lomborg are included in responses to Tom and/or Philbelow.

With regard to Mars you can't use an unproven Gaia Hypothesis to prove anything on Mars. It also seems to me rather contradictory to claim that an absence of CH4 indicates a lack of life and that the surface of Mars is oxidative. If Martian life lives below the surface in resevoirs of liquid water, small amounts of methane generated could easily be oxidized to CO2 and water by the surface chemistry. The recent Altacama results should make it quite clear that just because one region of a planet is oxidative and sterile does not mean all areas are. On Earth life dominates and is absent in few areas. On Mars, sterility probably dominates even if it is not complete.

Regards,
Mark