From: mig73allenford2002@yahoo.co.uk   
      
   Grenville Turner, who died 22 August, 2024, aged 87, was a geochemist   
   who jointly invented a method of radioactive dating used on rock samples   
   brought back from the moon.   
      
   The argon-40/argon-39 method of radioactive dating, invented by   
   Grenville Turner and his American colleague Craig Merrihue in the   
   mid-1960s, provided the technique to precisely date the tiny but   
   irreplaceable rock samples brought back by the astronauts of the Apollo   
   moon-landing programme. Turner pioneered the method prior to becoming   
   one of the few British scientists to be employed by Nasa as a principal   
   investigator on the Apollo programme.   
      
   https://www.theguardian.com/science/2024/sep/20/grenville-turner-obituary   
      
   Argon-40/argon-39 dating is similar to an earlier technique called   
   potassium/argon dating. In volcanic rocks and minerals any of the   
   isotope potassium-40 (the parent isotope) that is present decays over   
   time to the isotope argon-40 (the daughter isotope). Measuring the   
   amounts and ratios of each allows geologists to calculate the age of the   
   rock sample. However, the process was somewhat cumbersome.   
      
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