XPost: sci.geo.geology, alt.sci.planetary   
   From: g_d_pusch_remove_underscores@xnet.com   
      
   "hrtbreak"  writes:   
      
   > "Richard I. Gibson"  wrote in   
   > message news:40188646.50308@SPAMearthlink.net...   
   >> hrtbreak wrote:   
   >>   
   >>> Would one expect to see carbonates fixed in rocks when the atmosphere   
   >>> is rich in CO2?  Doesn't the large-scale fixation of CO2 in our   
   >>> atmosphere into rock formations require living organisms, like diatoms?   
   >>   
   >> Not to criticize your other speculations, but diatoms secrete   
   >> siliceous tests, not carbonate.  There are other critters, of   
   >> course, that DO turn CO2 into CO3 in rocks.   
   > ---clip---   
   > See speculation qualifications below.  My point was that if there were   
   > carbonate-based rocks in large quantities, would there be all that free CO2   
   > left in the atmosphere?   
      
   If Earth-life hadn't happened to accidentally stumble across the trick   
   of spewing out the nasty toxic poison waste-product gas called "oxygen,"   
   Earth's atmosphere would still have even _MORE_ CO2 in it than Mars's ---   
   and it took earth-life over a billion years for it to stumble across   
   _that_ particular trick!   
      
      
      
   -- Gordon D. Pusch   
      
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