The «Canals» of Mars

The "canals" of Mars were long, straight linear features reported by Italian astronomer Giovanni Schiaparelli in 1877 as canali (meaning channels or grooves), which were later mistranslated as "canals". Though popularized as evidence of an advanced civilization by Percival Lowell, these markings were proved to be optical illusions and, at most, natural geological formations like craters or canyons, disproven entirely by NASA Mariner 4 images in 1965. 

Edward Walter Maunder (12 April 1851 – 21 March 1928) was a British astronomer. His study of sunspots and the solar magnetic cycle led to his identification of the period from 1645 to 1715 that is now known as the Maunder Minimum. He observed the planets, and in a famous experiment demonstrated that the “canals” on Mars, claimed by Lowell and other observers, were optical illusions.