Comets, impacts and atmospheres II. Isotopes and noble gases Available to Purchase

We suggest that impacts by icy planetesimals during the first billion years of solar system history played a major role in the origin of planetary atmospheres. In the outer solar system, the effect of these planetesimals is evident in the super‐solar values of C/H and the variations of D/H in giant planet atmospheres. Laboratory experiments on the trapping of noble gases in ice forming at various temperatures provide an illuminating interpretation of noble gas abundances in the atmospheres of the inner planets, again implicating icy planetesimals. This model can be tested by searching for noble gases in comets, by investigating abundances and isotopic ratios in Jupiter’s atmosphere, and by further studies of the SNC meteorites and the atmospheres of the inner planets.