The universe has billions of galaxies. A few tonnes of meteorites fall onto Earth each day. Most dated meteorites are 4.55 by old. C first half BY . 20 Ne is non-radiogenic.
Ne ratio is substantially higher in atmosphere compared to solar abundance.
He is a good evidence for modern degassing because 3 He escapes the present atmosphere, hence the only ones present must be primordial. Rate of modern degassing integrated over time will not produce the total mass of the atmosphere. Hence, we know that degassing rate must have been faster then than it is today. In the present day Earth, there is only one primary mechanism of supplying NEW components to the atmosphere and that is volcanic degassing. If you take the metallic Fe out, system can migrate to higher fO 2 .