Further to the post www.sis-group.org.uk/news/hydrogen-and-water.htm … on November 11th we have an article in an Australian source on the subject – see https://cosmosmagazine.com/geoscience/geophysicists-propose-new-theory-t… … which actually is the same story but in a more coherent form. They refer to a paper in the Journal of Geophysical Research:Planets by Steven Desch from Arizone State University (which is where this subject started out but was sidetracked by other theories, water from asteroids). Desch says many scientists have supported a theory Earth's water came from asteroids, primarily because the rate of deuterium, a heavier hydrogen, in isotopes, is somewhat similar between the water in our oceans and hydrogen in asteroids. Desch says this is not the whole story. The ratio is close – but not fully so. Further, hydrogen deep in the earth has notably less deuterium – hence must have a potentially different source. The noble gases helium and neon, with isotopic signatures inherited from the solar nebula, have also been found in Earth's mantle. In the new study, we are told, several billion years ago, large watery asteroids developed into planets – such as the earth.
Through a process called isotopic fractionation, hydrogen was pulled or attracted to Earth's centre etc. This new model, it is proposed, would have earth with noble gases deep inside its mantle and a lower deuteronium hydrogen ratio nearer the core, suggests water is likely to occur on any large rocky exoplanet in extra-solar systems. In addition, this supports the idea that water or hydrogen is present inside Mars and the Moon. It would seem, as already deduced in the earlier post, there are two theories and the new one is that water/hyrogen arrives during the formation of the Earth, and in the other, it arrives during the asteroid bombardment theory (between 4.5 and 4 billion years ago). Inm other words, it is a moot point that we actually need an asteroid bombardment – another theory that seems to have a life of its own.