Formed 4.5 billion years ago, Mars once had a vast ocean that spanned the entire upper hemisphere, but this era gave way to long, frozen ages that saw its atmosphere steadily thinning and leaking away into space. Could it have ever contained life? Presenting a tantalizing vision of our nearest neighbor, planetary geologist Simon Morden discusses its dramatic history and astonishing present.

"Morden's writing style is friendly and accessible, and his excitement for the subject shines through. It's impressive how much information he packs into a narrative that flows so easily…. An excellent overview."—Booklist