From: henry@spsystems.net   
      
   In article ,   
   Norman Silverstone   wrote:   
   >> And indeed, the big snag is availability.  If you want a thousand tons of   
   >> xenon, you simply can't get it in any reasonable amount of time...   
   >   
   > As a matter of interest could anyone say how much Xenon is actually   
   > available and, when it is removed from the air, how is it replaced.   
      
   Xenon abundance is 87 parts per billion, and since we have about ten tons   
   of atmosphere per square meter of Earth's surface, a quick calculation   
   says there's roughly 450 million tons of xenon in the atmosphere.  It's   
   chemically inert for practical purposes.  Loss rate to space should be   
   insignificant for such a heavy gas.  There may be some xenon outgassing   
   from Earth's interior adding to the atmospheric content.   
      
   When it's removed from the air, nothing replaces it.  If it's used on   
   Earth, it eventually finds its way back into the atmosphere (that small   
   portion which isn't recycled -- xenon is expensive enough to be worth   
   careful recycling).   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)