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“We shall not cease from exploration and the end of all our exploring will be to arrive where we started... and know the place for the first time.”

– T.S. Elliot

This book is about a unique corner of the Universe, a small expanse of largely empty space that surrounds an ordinary star in the suburbs of the Milky Way galaxy. Known as the Solar System, this region is populated by the Sun, eight planets, dozens of satellites and dwarf planets, and a multitude of smaller objects.

Why is it important to explore and understand the Solar System? Because the third planet from the Sun is our home: Earth is the only place yet discovered where living organisms and intelligent life exist, or have ever existed. This unique “Goldilocks” world is the cradle of humankind, a fragile oasis in the vastness of space.

However, spaceship Earth is subject to many threats and stresses. Some are human‐made, such as deforestation, atmospheric pollution, or emissions of ozone‐destroying chemicals. Some are natural planetary processes, such as crustal movement and changing sea level. Others are external, including solar flares and marauding asteroids.

As news reports of natural disasters constantly remind us, Earth is an ever‐changing world, subject to ice ages, hurricanes, earthquakes, volcanic eruptions, and devastating cosmic impacts. Since its birth some 4.5 billion years ago, the planet has endured all of these natural forces to evolve into the largely benign place we see today. If we can understand how this evolution occurred, then we will have a better chance of predicting how it will change in the future.

This is where studies of the Sun, planets, and other inhabitants of the Solar System come to the fore. Only by comparing and contrasting the evolution of these very different objects can we hope to understand the past, present, and future of our Earth.

This scientific endeavor has been made possible by the advent of the Space Age. During this great age of discovery, modern technology has enabled us to construct automated spacecraft and robots that can act as surrogate explorers, venturing forth into the vast, hostile ocean of space to seek out and study new worlds.

Over more than half a century, hundreds of robotic spacecraft have been sent from Earth to examine at close quarters all of the planets, and many other objects, in our Solar System. This book is based on the flood of data sent back by these probes, which has enabled scientists to assemble, piece by piece, a realistic picture of our Solar System. For the first time, human eyes have been able to see towering cliffs, dust devils, erupting volcanoes, dry river beds and ice formations on dozens of distant worlds, most of them totally alien to our experience here on Earth.

Many years ago, my imagination was captured by books that described the family of alien worlds that circle our Sun, although, at that time, most of the information available was pure speculation. I have been fascinated by the many and varied members of the Solar System ever since. It is my hope that readers of this book will be similarly fascinated and inspired.

Exploring the Solar System has been written as an introductory text book for undergraduate students with a modest background in science. However, it is also intended to inform and inspire anyone who looks up at the night sky and wishes to know more about the alien worlds that inhabit our corner of the Universe.

After an introductory chapter which provides an overview of the Solar System, the book sets out to systematically describe the main characteristics of each major planet and its retinue of satellites, as well as the smaller members of the Sun's retinue. The final chapter enables the reader to compare and contrast our Solar System with systems around distant stars, where huge numbers of strange and exotic exoplanets are now being discovered.

Questions at the end of each chapter have been added to help students to recognize and comprehend the main points of each chapter, and to compare each planetary system. Useful reference material is provided in the form of numerous appendices, an extensive reading list, and a comprehensive glossary.

This book would not have been possible without the support and encouragement of Ian Francis, Senior Commissioning Editor for Wiley‐Blackwell, and Delia Sandford, the Managing Editor for this project. I am most grateful for their patience and forbearance as the book has edged towards completion.

My sincere thanks also go to Kelvin Matthews of Wiley‐Blackwell, who has checked all of the illustrations, to the production team, especially Kathy Syplywczak, and to the various reviewers whose helpful comments and criticisms played such an important role in shaping the final text.

Much of the information in this book is based on original scientific papers, many of which are listed in the final pages. Numerous other sources – many now available on the Internet – were also used, including magazine articles, press releases, and other information provided by space agencies – particularly NASA ‐ and universities. I am also very grateful to everyone who helped me to obtain, or provided me with, the spectacular images that illuminate this story of outreach and discovery.

Finally, I would like to thank my wife, Edna, who first encouraged me to describe and explain the wonders of our Solar System.

Peter Bond