The "Canals of Mars" refers to a network of linear features observed on the surface of Mars in the late 19th and early 20th centuries. These features were initially thought to be artificial waterways created by hypothetical Martian civilizations. The term was popularized by astronomer Percival Lowell, who believed these canals were evidence of advanced life on the planet. Later observations and research revealed that the canals were optical illusions caused by the planet's surface characteristics and atmospheric conditions. Modern exploration, including data from rovers and orbiters, has shown that Mars has no canals, but it does have ancient riverbeds and signs of past water flow.