[30] Specifically, xenon is useful for calculations of water reduction after some time. Not just could it be a noble fuel (and thus will not be removed from the atmosphere by chemical reactions with other elements), but comparisons amongst the abundances of its 9 secure isotopes in the modern environment https://kevalaniru.com/port-town-wakes-up-to-15-year-ban-on-pet-bottles-plastic-carry-bags/