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There are a few other general points I'd like to make about the chapter contents of the textbook. You will notice that the units I use in the textbook are not consistent throughout. For example, growth temperatures of microorganisms are usually shown in Celsius. Temperatures of planetary surfaces are often expressed in Kelvin. Different scientific fields tend to use different units, and, rather than creating complete consistency (which would result in seemingly odd units being used for phenomena where they are not normally used), I have stuck with the normal conventions. These differences highlight the multidisciplinary nature of astrobiology.

In all the chapters, I have included some other information shown in boxes. Some of the boxes present points of debate in astrobiology that are worth discussing with others or contemplating yourself. These “Discussion Points” are an opportunity to get you to think about ideas in different fields that link to astrobiological questions. I have also written them in places where the material might seem very conventional. I hope they will stimulate you to think about the material being described in new ways. For example, is the biochemical structure of life on Earth something universal or a very particular outcome of Earth's experiment in biological evolution? Such a question should encourage you to think about what the basics of biology might, or might not, tell us about life elsewhere, if it exists. I have attempted to provide some similar thoughts and questions in all the chapters. The content and questions in these boxes are by no means exhaustive, and you should use them to encourage other discussions or come up with new questions. In particular, try to think about questions that bridge different chapters and the different fields in the book.

Here and there I have included some textboxes about some of the major facilities that astrobiologists use. There are a vast number of techniques that astrobiologists employ in the laboratory, but some large facilities, coordinated internationally, such as space telescopes, expand the reach of the science significantly. They also give you a flavor of the modern nature of international science.

I have included some further reading. This was, perhaps, the most difficult task. It is impossible to do justice to all the literature that exists in every field that comprises astrobiology, let alone list all the main contributions. Instead, I've suggested two or three popular and/or technical books that relate to each chapter that might provide some enjoyable additional reading. I have also listed a set of papers. They are papers I think will give a representative sprinkling of just some of the possible avenues an interested reader might pursue and that relate to the main themes and subjects covered in each chapter. Again, no significance should be placed on the omission of many important papers or the inclusion of the ones listed.

At the end of each chapter, I have provided some questions for review and reflection. The answers to these questions are within the chapters themselves and do not require new information. Their purpose is to offer a means for some structured review of the chapter content and to help consolidate your knowledge. Even if you choose not to produce written answers, you might like to read them and ponder the answers as a way to ensure you have grasped the main ideas in each chapter.

There is yet another dimension of astrobiology that I have touched on in this book. I often get asked by students, “What degree do I need for astrobiology? What field should I take an interest in to become an astrobiologist?” Any degree allows a person to explore aspects of astrobiology from different angles. Science should never be closed to inquisitive minds on account of narrow human discipline definitions. Throughout the book, I've included sections that contain some personal information about a selection of astrobiologists, particularly colleagues early in their careers. I've shown their original degree areas, what motivates them, and how they got into astrobiology. Their career interests are not necessarily directly aligned to the subject of the chapter in which they appear, but their stories are distributed throughout the book. There are many fine people in astrobiology, and I'd like to emphasize that there is no significance to my selection or omission of these astrobiologists. I chose a selection of outstanding colleagues whom I thought would exemplify the variety of disciplines from which astrobiologists are currently launching their careers.