Previous Searches for Intelligent Civilizations
The Moon (H.G.Wells, Jules Verne), Mars (H.G.Wells) and Venus have been the favorite sites of early literary works on extraterrestrial inhabited worlds or destinations for interplanetary voyages.
Scientific speculation about Mars and its inhabitants
goes back at least 100 years ago when the astronomer Giovanni
Schiapparelli, using a 9 inch telescope, claimed to have found
numerous canals criss-crossing the surface of Mars. The regularity of
the pattern of these canals suggested to him that they were artifacts
of a civilization. To be specific, he called these canals, "canali" -
a word that in Italian has both the meaning of "channels" and
"canals". The latter word was used in the publicization of his
discovery when his work was reported through English language media;
thus, the use of the word "canals" implicitely suggested that these
features on the planet Mars were made by intelligent beings and were
not the product of weathering.
Percy Lowell, an amateur astronomer who funded the Lowell observatory in Arizona, was a convinced propenent of the existance of of artificially-made "canals" on Mars. Later on, it was demonstrated that features of the size of canals couldn't have been resolved with the power of telescopes avalialble at the time of the discovery (and they are still not possible to resolve today). Thus, the canals were optical illusions, or rather the product of the work of the human brain that tries to "make sense" of a visual pattern. In this case, the brain resolved a pattern of lights and shadows, perhaps caused by dust storms, in terms of a grid of lines, the "canals".
Pictures taken from spacecrafts, such as the Mariners and then the Voyagers, dispelled any residual hope of seeing the canals on the surface of Mars.
Another prominent feature that people have "seen" on Mars, is a
formation of rocks that stunningly looks like a human face. Proponents
of the "Mars Face" claimed that a civilization carved rocks on Mars to
make the "Face", as the mysterious dwellers of Easter Island did with
the erect human-like figures.
See this site for further information
Examination of the "Face" during different periods of time under different lighting conditions reveal that the "Face" deosn't quite look like a face after all. In reality, no sign of even the most primitive form of life has been found by the Voyager probe that landed on Mars, and the possibility that past life exsisted is rather controversial at the present time, see section Hot Topics for more details.
Search for signs of primitive life in the Solar System continues (See Search for Life inside the Solar System. But to find signs of intelligent life, our search has to take us to planets orbiting other stars. With the advent of radio communications at the beginning of this century, and especially after WWII, astronomers started to scan the skies for radio signals from other civilizations, as summarized in the next section (see the "others" section to your left). A review of current searches is given in Current Searches.