In astronomical terms, the Solar System is our backyard. Set against the vast number of stars in our Galaxy, the colossal number of other galaxies in the observable universe and the incredible distances involved, our Solar System is an extremely tiny part of the Universe. However, this is where we live. It is where life on Earth developed, and it gives us our only vantage point from which to view the rest of the Universe.

Unlike other planetary systems, the objects in our Solar System are close enough to visit with space probes and to study long-term and (in some cases) in reasonable detail using telescopes. As well as revealing the splendour and diversity of the worlds that make up the Solar System, these studies allow us to try and understand ‘what makes the Solar System tick’. By doing this, we not only attempt to understand the system in which life evolved, but also gain an insight into the likely diversity of individual planetary bodies and their possible histories all over the Universe.

One of the more fundamental questions often asked is, ‘why is the Solar System the way it is?’ In answering this question, we have to address more detailed questions such as, how were the planets made? What were the planets made from? Were all the planets made from the same material? Why do they look so different? Do all the planets have the same internal structure? Does their surface appearance change with time? The answers to these questions lie in the physical and chemical processes that act on the bodies within the Solar System. Understanding these processes allows us to appreciate how the planets and the other Solar System bodies have formed and have been changed over time, and hence why they look the way they do today. In this book, you will be looking at these processes in detail.