title: Decline and fall of the empire.
abstract: "Are they worlds, or are they mere masses of matter? Are physical forces alone at work there or has evolution begotten something more complex, something not unakin to what we know on Earth as life? It is in this that lies the peculiar interest of Mars." Percival Lowell (in ref. 1, p. 3)
authors.affiliation: NASA Ames Research Center, Moffett Field, California 94035-1000, USA.
authors.forename: K
authors.initials: K
authors.lastname: Zahnle
mesh_terms: D001256:Astronomy / Q000266:history*; D018559:Exobiology; D005118:Extraterrestrial Environment; D049672:History, 19th Century; D018535:Mars; D014481:United States