From: '''newspam'''@nonad.co.uk   
      
   On 31/12/2025 16:06, john larkin wrote:   
   > On Wed, 31 Dec 2025 11:01:50 +0000, Martin Brown   
   > <'''newspam'''@nonad.co.uk> wrote:   
   >   
   >> On 29/12/2025 16:04, john larkin wrote:   
   >>> On Mon, 29 Dec 2025 18:43:12 +1100, Bill Sloman    
   >>> wrote:   
   >>>   
   >>>> On 29/12/2025 3:17 am, john larkin wrote:   
   >>>>> On Mon, 29 Dec 2025 03:08:19 +1100, Bill Sloman    
   >>>>> wrote:   
   >>   
   >>>>>> John's not entirely correct. There are meteorites that have fallen to   
   >>>>>> earth that seem to have been kicked off Mars.   
   >>>>>   
   >>>>> "Seem to" !   
   >>>>>   
   >>>>> The theory is good for selling museum tickets.   
   >>>>   
   >>>> As the wikipedia page points out, the trace element profiles match those   
   >>>> seen by the Mars rover.   
   >>>>   
   >>>> It's be better founded theory than you want to acknowledge, probably   
   >>>> because you haven't got a clue about the science that backs it up.   
   >>>   
   >>> Oh, I've worked with TOF atom probe spectroscopy and backscatter   
   >>> analysis and analytical NMR and all sorts of exotic physics.   
   >>> Physiscists need help with circuits.   
   >>>   
   >>> But a lot of the solar system has rocks with similar isotopic content.   
   >>> Declaring a meteorite to be a chunk knocked of Mars is a real   
   >>> hand-waver.   
   >>   
   >> Not really. The oxygen isotopic signature on Mars is different enough to   
   >> recognise Mars rocks. Although that doesn't stop charlatans on eBay   
   >> selling Mars meteorites that are just similar looking Earth rocks.   
   >>   
   >> Anyone with a stable isotope MS or a noble gas MS would be able to test   
   >> the gasses in inclusions and see old Martian atmosphere if it is real.   
   >   
   > Wouldn't therre be a lot of diffusion in billions of years?   
      
   Some of them are geologically speaking relatively young.   
      
   They have Martian meteorites where the inclusions contain gasses in   
   about the same ratios as Viking measured and more importantly with the   
   same isotopic ratios for Oxygen and Carbon as Mars has.   
      
   The gas inclusions that the geologists target are typically in zircons   
   (which are practically indestructible once formed) and not much diffuses   
   through or into them. Helium might possibly but the other noble gas   
   atoms are just too big. The time of last melting is one of the important   
   things that can be uniquely determined for any rock/ceramic/glass by MS.   
   The point in time where stuff from radioactive decay remains trapped.   
      
   https://en.wikipedia.org/wiki/Uranium–lead_dating   
      
   > Same for ice cores.   
      
   Ice cores are surprisingly good at preserving past atmospheres trapped   
   at the time that the snow fell and then compacted. The Oxygen isotope   
   ratios in ice itself and in stalagtites are a good proxy for global mean   
   temperature. The lighter forms of water molecule are slightly more   
   volatile and preferentially collect as solid ice at the poles leaving   
   the seas and rain elsewhere enriched in the heavier isotopes.   
      
   --   
   Martin Brown   
      
   --- SoupGate-DOS v1.05   
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