NASA’s latest Mars rover, Curiosity, seeks to answer a single question: Is the planet habitable? The public’s fascination with the possibility of life on Mars began in the late 19th century, when an Italian scientist reported seeing “canals” on the planet’s surface. Astronomer Percival Lowell subsequently envisioned a utopian society there, while author H. G. Wells painted a picture of marauding Martians invading Earth. As Curiosity rolls across the dusty plains of the Red Planet, explore five key events that fueled our obsession with finding life there.