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Who popularized the idea that canals on Mars were built by intelligent beings?

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Mars
Mars An especially serene view of Mars (Tharsis side), a composite of images taken by the Mars Global Surveyor spacecraft in April 1999. The northern polar cap and encircling dark dune field of Vastitas Borealis are visible at the top of the globe. White water-ice clouds surround the most prominent volcanic peaks, including Olympus Mons near the western limb, Alba Patera to its northeast, and the line of Tharsis volcanoes to the southeast. East of the Tharsis rise can be seen the enormous near-equatorial gash that marks the canyon system Valles Marineris.

The American astronomer Percival Lowell was the primary figure who popularized the theory that the linear markings on Mars were artificial canals constructed by intelligent beings.12

While the Italian astronomer Giovanni Virginio Schiaparelli first reported observing these features in 1877 and termed them canali (meaning "channels"), he used the word in a neutral sense. It was Lowell who, around the turn of the 20th century, championed the idea that these markings were massive irrigation systems designed to transport water from the planet's polar caps to equatorial regions.132

Modern science has since determined that these "canals" were optical illusions resulting from the human eye attempting to resolve natural surface featuresā€”such as crater chains and ridgesā€”at the limits of telescopic visibility. Spacecraft missions, beginning with Mariner 4 in 1965, confirmed that no such artificial networks exist on the Martian surface.12