A Martian Sensation: Maps, delusion, and the Mars Canals

The planet Mars is named after the Roman god of war, as highlighted in this illustration from a nineteenth century astronomy schoolbook. The eight drawings of the planet show several features reportedly observed through telescopes between the seventeenth and nineteenth centuries. Until the 1830s, the permanence, and even the reality, of such features was a matter of debate. Once astronomers ascertained that at least some of the features were stable formations, mapping Mars became a legitimate endeavor.

Roughly every 26 months, Mars is in opposition, which is when the planet is closest to Earth. Oppositions of Mars were keenly anticipated by astronomers because they provided a great opportunity for observation. These drawings were made by the Rev. William Rutter Dawes during the opposition of 1864. Despite his severe myopia (nearsightedness), Dawes excelled with the telescope and set a new benchmark for the study of Mars.   

Beginning in 1877, Giovanni Schiaparelli carried out extensive observations of Mars during opposition, and produced several maps of the red planet. He used the term “canali” to refer to features that, to him, looked like geographical straits, which can be clearly seen in this map from 1888. "Canali" was translated to English as "canals", suggesting artificial waterways instead of naturally occurring features. In addition to this mistranslation, renditions and maps of Mars and its "canals" were pivotal in sparking speculation and debate about a hypothetical Martian civilization.

Percival Lowell became a committed investigator and advocate of the Mars canals (shown here), adding more than a hundred to the “canali” previously identified by Schiaparelli. Lowell believed that a Martian civilization had built a network of canals to fight aridification through the redistribution of water from the polar ice caps. These ideas were discredited by several astronomers, but they ignited the public imagination as they made their way into newspapers and popular magazines.  

Astronomers traveled far and wide to observe Mars in opposition.They sought places with good visibility and where the planet reached higher altitudes in the sky. Percival Lowell was particularly active in searching for observing sites abroad. He established an outstation in Mexico (shown here), and financed an expedition to Chile. These endeavors resonated with the adventurous geographical expeditions of the turn of the twentieth century, reinforcing the image of Mars observers as intrepid explorers of an alien world.

In an age when the Earth’s empires were mapped with ever greater detail, maps of Mars, with their own coordinate grids and nomenclature systems, conveyed a similar sense of accuracy and authority to those of Earth. Such is the case of this map of Mars by Percival Lowell, originally assembled in 1897, which suggests a planet cleverly engineered by intelligent Martians (note the intricate network of canals), and mapped from afar with great acumen by an expert earthling.

Eugène Antoniadi, a supporter of Lowell for years, observed Mars during the opposition of 1909-1910 with a 33-inch instrument at the Meudon Observatory in France, by then the largest telescope in Europe. In moments of good visibility Antoniadi could see the supposed “canals” were in fact myriads of discrete features, as illustrated here. It became clear that the canals were nothing more than an optical illusion.