From: bill.sloman@ieee.org   
      
   On 1/01/2026 12:31 am, Martin Brown wrote:   
   > On 31/12/2025 11:32, Jeroen Belleman wrote:   
   >> On 12/31/25 12:01, Martin Brown wrote:   
   >>> On 29/12/2025 16:04, john larkin wrote:   
   >>>>   
   >>>> 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.   
   >>   
   >> I suppose analysis methods are more refined these days, but in 1974 I   
   >> simulated a meteorite hit in a class mate's garden as a hoax. What I   
   >> did not anticipate is that everyone took this seriously. It was just a   
   >> piece of steel furnace slag, but even the Max Planck institute in   
   >> Germany refused to admit they'd been fooled.   
   >   
   > Back then they wouldn't have any easy way of testing it. That all   
   > changed in about 1990 when TOF ion probes and laser ablation mass   
   > spectrometry came of age. Before that you had to pound it to dust and   
   > dissolve in HF (not nice) then do some very fancy wet chemistry.   
      
   Not true. Back when I was an undergraduate I had to check out an X-ray   
   fluorescence scheme for detecting low levels of alumina (Al2O3) in   
   titanium dioxide (TiO2) for my summer job, in 1961. As a graduate   
   student I met Alan Walsh (in 1968) who pretty much invented atomic   
   absorbtion spectroscopy, where you sprayed the solution into a flame and   
   detected the absorbtion lines of specific elements in the flame.   
      
   Australia's plastic banknotes have holograms as a side effect his   
   efforts to make cheap plastic diffraction gratings to disperse the light   
   that had been through the flame.   
      
   Inorganic chemists took to physical methods early.   
      
   > I worked on software for the mass spectrometric rare earth element   
   > analysis of meteorites at one time (and on dating ancient rocks).   
      
   Mass spectrometers work, but you need big expensive precise machines to   
   sort out the isotopes of heavier elements (and I didn't work on them   
   until 1992, and then only briefly).   
      
   > The geologists get very excited about the Europium anomaly in them. That   
   > one species is a marker that varies enormously with the type of rock and   
   > the chemical environment when and where it was formed.   
   >   
   > https://en.wikipedia.org/wiki/Europium_anomaly   
   >   
   > I understand that it occurs when Europium is in an unusual oxidation   
   > state and is commonly seen in stony chondrites and moon rocks. I have   
   > seen a few close up in a glove box. I never had the chance to smell any.   
   > Keeping them clean under an inert dry atmosphere was a priority.   
   >   
   > Cute demo with a modern Nd magnet you can collect micrometeorites from   
   > the black gunge that accumulates in PVC gutters. Too small for the naked   
   > eye to see but obvious with even a basic toy microscope.   
   >   
   > https://www.quekett.org/resources/article-archive/bsw-2017/bsw   
   7-micrometeorites   
   >   
   > Some nice almost safe for modern H&S rules science demos on that site.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)