In the 19th century, the astronomer Giovanni Schiaparelli claimed that Mars was covered by a network of channels. Many people believed that these were canals created by an intelligent civilization to help carry water from the Polar Regions to drier areas around the Equator. Recent photographs of Mars have shown that there are many channels on the planet, but scientists believe these were created naturally by running water billions of years ago.
The space-heads among you have undoubtedly heard about the Curiosity rover’s first significant discovery: the remnants of an ancient streambed on Mars, which would seem to indicate the presence of water in the planet’s history. This jagged pile of alluvial rock and dust my not took like much, but it brings to mind one of my favorite pieces of Martian historical arcana.
For a time in the late 19th century, it was believed that there were canals on Mars. The Italian astronomer Giovanni Schiaparelli, who observed Mars in 1877, was the first to describe, name, and lovingly illustrate mysterious straight lines along its equatorial regions, which he called canal. Viewed with the telescopes of the day, in brief instances of still air amidst the optical strangeness of atmosphere, Mars was tough to figure. There are areas which appear darker or lighter (these are called Albedo features); to an enthusiastic observer, it was easy to speculate of continents, oceans, or even straight-line canals.
Beset by the same optical illusions, many astronomers seconded Schiaparelli’s observations. The maps of the day show a Mars riven with peculiar webs and lines–lines which successive high-resolution mapping of the planet have definitively shown do not exist. The mechanism that caused this illusion appears to be internal: faced with a shifting landscape of foggy forms, glimpsed at through simple lenses of glass through the refractive index of Earth’s atmosphere, the human brain tends to impose order.
The persistence of belief in Martian canals is often attributed to a linguistic fluke, that the Italian canal, meaning “channel” (or watercourse, and not necessarily of unnatural origin), was mistranslated to the English “canal.” I really love this narrative of language shaping reality, but unfortunately it’s the astronomical equivalent of an urban legend. “Canal,” in fact, was used in the earliest English accounts, and Schiaparelli made no move to correct the misunderstanding, if he was aware of it.
