Using the "Parallel Lives" approach adopted by the Greek biographer Plutarch, noted historian of astronomy William Sheehan contrasts the lives and research careers of two famous astronomers, Percival Lowell and Edward Emerson Barnard. Drawing on vast archival materials and hitherto unpublished source materials, Sheehan documents in detail the contributions of these two late 19th and early 20th astronomers. Living at a time when controversies about Mars peaked, when great observatories were being built, and when research increasingly turned away from the Solar System toward the stellar and extra-galactic universe, these observers made spectacular contributions to astronomy. Their work still inspires, and continues in Perseverance rover's explorations of the surface of Mars carrying forward Lowell's dream of showing that Mars may once have been "the abode of life," and in Barnard's pioneering wide-angle photographs of the Milky Way which first showed the sweep, majesty and complexity of the Galaxy. The work of decades of research and writing, Sheehan has produced what is likely to become the definitive work on these two great astronomers. "Parallel Lives marks an important contribution to the history of astronomy. The book is masterful and inventive. William Sheehan could hardly have chosen two more compellingor contrastingpersonalities to analyze in this fascinating dual biography." - David Baron, author of American Eclipse and The Martians, and former Chair in Astrobiology at the Library of Congress. "Sheehan has united scientific acumen, detailed historical research, penetrating insight into character, and narrative virtuosityand adapted it all to an ancient Greek modela remarkable achievement!" - Michael Armstrong, Assoc. Prof. Emeritus of Classics, Hobart and William Smith Colleges, Geneva NY William Sheehan's many books include the authoritative biography The Immortal Fire Within: The Life and Work of Edward Emerson Barnard and (with Jim Bell) Discovering Mars: A History of Observation and Exploration of the Red Planet, which has been called the "gold standard of books on Mars" (Michio Kaku).