The canals had been sky areology, and many more bad hypotheses had been formulated in the same way, hypotheses that were only now being tested with the rigor of ground areology. Most collapsed under the weight of surface data, got tossed in the canal as they said.
There is some strong old time science fiction, written by guys like Robert Heinlein, that included the Canals that Percival Lowell was convinced that he had seen. Lowell fueled the imagination of Edgar Rice Burroughs to create the hero John Carter of Mars. Nadia's joke earlier, about being a Princess of Mars was a Burroughs reference.
Robert Heinlein so loved the idea of Timeless Martians ctiss-crosding their world with canals that he continued using the idea in his science fiction into the 1980's, long after we knew that Mars held no canals or, sadly, Martians.
