First the hook and then the science: Source: "Lethally Hot" Earth Was Devoid of Life—Could It Happen Again? Thanks to Google, I'm finding a rich source of proxy articles to study. The initial scans report water using these different isotopes have differential rates of evaporation. So the ratio of these isotopes in fossilized minerals would give an indication of relative temperatures. That these isotopes are stable lover these time lines, well there is a lot to read. Bob Wilson
