Readers who are shopping for a great book to read, who are trying to decide whether to read past page one in Life on Mars, likely will turn first to the Table of Contents, where I have what I hope are a few alluring chapter titles (Why Mars Matters; Water on Mars: the Real Deal; Vikings on the Plains of Chryse and Utopia) and then to the first lines on the first page. Authors, after all, lose sleep in their efforts to make sure the first line and first paragraph of the first page is so well written and so enticing that readers are drawn into reading more. So, of course, I think readers should start at the beginning of Chapter 1. But I’m neither Charles Dickens nor Herman Melville, and though I like my first sentence (“Are we alone in the universe?”), I know I can’t compete with “It was the best of times, it was the worst of times” or “Call me Ishmael.”Where then, to best lure potential readers into Life on Mars? The epigram, penned by Canadian astronomer Peter Millman in 1939, encapsulates the value, intrigue, and importance of the chapters that follow in such a way that I would advise readers to start their journey there, after the Table of Contents but before page one. In fact, I feel so strongly about this that I’ll offer the epigram to readers right here: “So much nonsense has been written about the planet … that it is easy to forget that Mars is still an object of serious scientific investigation.” Mars is the closest place in the entire universe where extraterrestrial life might exist. Life on Mars, if it exists, could be DNA-based and thus could be the parent or the child of terrestrial life, or, life on Mars could be a form of biology that arose independently of life on Earth. Those are serious questions about what we know and don’t know about life on Mars. The answers to those questions are extremely important for understanding ourselves and for evaluating the next steps humans should take as we set sail from Earth to other ports of call. And what was true in 1939 remains true today: much of what we think we know about Mars might be nonsense. I hope readers will want to dig into the pages of Life on Mars to unearth my reasons for making such a (potentially) controversial comment.NASA plans to send astronauts into orbit around Mars by the 2030s. Elon Musk wants to send colonists to land on Mars on a SpaceX rocket even sooner, by 2024. Jeff Bezos wants to use his Blue Origin rockets to put space adventurers into work in Earth orbit in the 2020s; he then plans to continue outward to the Moon and Mars. The folks at Mars One want to land permanent settlers on Mars in 2032. The ruler of Dubai has plans to build an entire city on Mars no later than 2117. Mars may well represent the future of humanity.Readers should understand that the days of science fiction regarding Mars are over. No more War of the Worlds, no more Martian Chronicles, no more Red Mars, Green Mars, Blue Mars. Humans setting foot on Mars, perhaps colonizing Mars and working to terraform Mars – all of these things could happen within a decade and almost certainly will happen within the lifetimes of many readers, unless very soon humanity collectively decides that we shouldn’t do any of these things.As we gear up for missions like these, we have a responsibility to think deeply about what kinds of life, if any, may already inhabit the red planet; also, the potential impact of injecting terrestrial biota into a possible Martian biosphere. Do we have an inalienable right to invite ourselves in? I hope my readers will spend some time deeply pondering their own answers to this question.