5. The “Moon Men” Hoax

In 1834, astronomer John Herschel journeyed to South Africa to set up an observatory to study the Southern Hemisphere sky. The next year, an upstart New York newspaper eager to increase circulation, The Sun, published a series of articles sensationalizing Herschel’s discoveries. The articles claimed the astronomer had sighted a race of “bat-men” on the Moon, with the creatures living in cities and temples made of sapphire. Rival newspaper editors frantically pursued the story, convinced they’d been scooped. Perhaps the tale wasn’t a stretch for some, as Herschel and many other prominent individuals at the time had professed belief of extraterrestrial life in the solar system. And the population at large seemed to believe the fantastic tale; one religious group even vowed to send missionaries to the Moon to “convert” the batmen. Several weeks later, as scientists began pressing the paper for more details, and rival newspapers started making up their own stories about the man-bats, The Sun confessed to the hoax.
4. Martian Canals

It seems hard to believe today, but mankind took it for granted in the late 19th and early 20th centuries that Mars was inhabited, thanks to the supposed observation of canals on the planet’s surface. In particular, astronomer Percival Lowell observed Mars at every opportunity, sketching and drawing extensive maps of the Red Planet. Lowell painted a portrait of Mars as a dying world, inhabited by a race that had built an extensive system of water works to preserve a precious resource. Keep in mind, in Lowell’s time, an astronomer still held a vigil at an eyepiece and hurriedly sketched fleeting detail during moments of good “seeing.” After Lowell’s death in 1916, astronomers agreed the concept of canals had been an optical illusion. Still, Lowell’s visions of Mars inspired some classic science fiction tales, including H.G. Wells’ War of the Worlds and Ray Bradbury’s The Martian Chronicles. The general acceptance of Martian life probably also explains the hysteria that gripped the population during Orson Wells’ infamous War of the Worlds broadcast in 1938. The theory that Mars might at least support a desert-like environment persisted right up to the first flyby of Mariner 4 in 1965.
3. The Discovery of Pulsars and “Little Green Men”

In 1967, astronomers Antony Hewish and Jocelyn Bell were surprised to encounter a radio source in the Crab Nebula that pulsated every 1.33 seconds. At that time, no natural source with such precision was known; the team even designated the source as “LGM-1,” for Little Green Men. Had evidence of an extraterrestrial civilization been discovered? One could easily imagine such a source as a sort of cosmic beacon, guiding and synchronizing a space-faring civilization or perhaps telling them to avoid some hazard. The source was later identified as something almost as bizarre — a pulsar, or the remnant of a neutron star's supernova explosion. Such an object is terrifically dense and about the size of a city, swiftly rotating and spewing energy from its poles. Some 1,800 pulsars have since been discovered. Several years after the discovery of that first pulsar, Bell noted that she did not seriously believe she’d found an alien signal, but that the concept raised some intriguing questions: “It is an interesting problem — if one thinks one may have detected life elsewhere in the universe, how does one announce the results responsibly? Who does one tell first?”
2. The “Wow!” Signal

Modern SETI searches began in 1960 with Project Ozma. One of the most interesting finds thus far occurred in 1977, when a research project based at Ohio State University received a 72-second signal over 30 times the intensity of the background noise coming from the constellation Sagittarius. Researcher Jerry R. Ehman wrote “Wow!” in the margins of the printout, and the name stuck. Terrestrial interference is unlikely, as the signal rose and faded as the array rotated along with the Earth, just as a space-based source would. No stars or sources exist near the location, and further attempts to locate the source have come up empty. Was the Wow! signal a brief focusing of an extraterrestrial signal, perhaps gravitationally lensed by a dark, intervening object? Here’s a link to Dr. Ehman’s theories and further searches for the Wow! signal’s source.
1. The Viking Spacecraft "Discovers" Life on Mars

In 1976, NASA’s two Viking spacecraft made the first successful landings on the planet Mars. Both contained an experiment designed to look for microbial life on the Red Planet. Tantalizingly, something in the soil seemed to “interact” with the chemicals in the experiment, just as life might in the process of metabolism. Many chalked this up to a geological process. Most scientists remain unconvinced, however, and the results of the Viking experiments are still hotly contested. Those results are still being studied — a report issued in April 2012 by a former NASA employee and neurobiologist found evidence consistent with life. Even the discovery of primitive life on Mars past or present would have huge implications, as it would mean that life must be fairly common in the cosmos. NASA’s Mars Rover Curiosity is set to land on the Red Planet in early August 2012 and will attempt to follow up on the Viking surface chemistry experiments with an experiment known as SAM, or the Sample Analysis at Mars.
One More: Hoax Touts Life on Martian Moons
On April Fool’s Day 1959, astronomer Walter Scott Houston claimed that the tiny moons of Mars were in fact artificial satellites, hollowed out and constructed by Martians. Though done as a prank, the “theory” was hypothesized in earnest by Soviet astrophysicist Iosif Shklovsky. The idea that many people seemed to take for granted that we shared our solar system with another intelligent species seems to suggest that if — or when — the initial discovery of extraterrestrial life breaks today, it’ll be business as usual. SETI researcher Seth Shostak raises the possibility that even if we detect an extraterrestrial signal, it may be years before we know very much about the other civilization. Of course, if they intend to meddle in our affairs, or land with their death rays blazing on the White House lawn, it might be another story.
