The Frost Line

 In the second chapter of this book, given the very nature of the ocean worlds, we delve into the origins of water within our Solar System and its profound influence on the diverse array of planetary bodies that inhabit it. Our exploration encompasses an examination of the methods employed to trace various types of water throughout our planetary neighborhood. Additionally, we provide insights into a fundamental concept essential for comprehending the dynamics of our Solar System: the frost line, alternatively referred to as the snow line or ice line. This boundary delineates the region within our Solar System where water and other volatile molecules transition from gaseous to solid states, thus becoming readily available as foundational constituents during the formation of planetary bodies. We review some of the latest finds on this such as the water discovered on comet 67P/Churyumov–Gerasimenko or asteroid Ryugu. We also try to understand how our Solar System has evolved with time, through the presentation of the Grand Tack hypothesis, and the implication for ocean worlds,