Lowell's theories quickly spread among the public and inspired science fiction writer H.G. Wells to write War of the Worlds. Taking his cue from Lowell, Wells envisions a dying Red Planet in the novel, with oceans that are drying up and resources that are thinning. To survive, the Martians invade Earth to rampage this planet's offerings.
Other writers soon followed suit with their own tales about Martians, including Edgar Rice Burroughs' A Princess of Mars and Ray Bradbury's The Martian Chronicles.
But as public imagination about the Red Planet grew, scientists were becoming more doubtful about the possibility of complex life on Mars as flyby spacecraft snapped images of a dry, desolate planet. Fantasies of a Mars civilization were quashed in 1976 when NASA got its first close-ups of the mysterious planet with the arrival of the Viking 1 orbiter and probe.
"That's when we knew for sure it was a rock-strewn place," says Launius." A lot of people were really disheartened."
Famed astronomer and thinker Carl Sagan was reportedly "never so depressed" in his life at the news. There was little hope now of finding any intelligent life on the planet, but the Viking probes did zero in on something the Italian astronomer had seen centuries ago — channels.
Could these gullies have been formed by ancient Martian rivers and oceans? Images from the Mars Global Surveyor and other craft have supported the idea and led to the new NASA motto: "Follow the Water."
If water exists or existed on Mars, many believe there could be evidence of past life or even primitive living creatures now on the planet. That idea was energized by the announcement in 1996 that astrobiologists had identified evidence of fossilized bacteria in a potato-sized Martian meteorite.
The theory has since come under severe scrutiny as other researchers analyze the meteorite, but the search for evidence of Martian life — in any form — has not died.
"Our expectations may have decreased over the past century," said Steven Dick, NASA's chief historian. "We're down from little green men to fossils from the past or bacteria just under the planet's surface. But that's still exciting."
As Mark Adler, the mission manager for NASA's Spirit probe, points out, there is much to learn about what lies on that mysterious red glow, more than 34 million miles away.
"Honestly," he says, "I have no idea what we'll see."