From: henry@spsystems.net   
      
   In article ,   
   R F L Henley  wrote:   
   >unless and until we have robotically established conclusively that there is   
   >or is not life on Mars, we can't put humans on the planet because they will   
   >inevitably bio-contaminate it.   
      
   Yes and no and maybe...   
      
   It's virtually certain that the surface itself is sterile, and that   
   terrestrial organisms released on it will die.  (Gil Levin is about the   
   only remaining holdout on this... and his case took another body blow   
   recently, when studies of soil from the ultra-dry region of the Atacama   
   desert revealed that *Earth* soils in such conditions have some sort of   
   non-biological oxidizing agent in them.)   
      
   It's likely that the immediate subsurface is the same way, but that has   
   not yet been confirmed, and needs to be.  Doing that before a manned   
   landing is reasonable and desirable, I would say.   
      
   Testing the surface and immediate subsurface over a wider range of Martian   
   terrains, notably including near-polar regions, would also be smart.   
      
   However, once that's done, a manned landing seems reasonable to me.   
      
   The odds are good that any extant Martian life is just about inaccessible,   
   e.g. underground in geothermal areas.  Given a little care, it ought to be   
   possible to conduct surface activities without contaminating areas like   
   that.  Moreover, it will be almost impossible to study areas like that   
   with robots, even with short-delay control from Mars orbit; human presence   
   on the surface is going to be needed.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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