The two astronomers themselves were at pains not to disrespect one another in correspondence or in publication, but it was obvious that the two maps could not both be correct. Both astronomers claimed to have been perfectly objective and to have made accurate maps, but the maps did not seem to be reconcilable in any way. Green suggested that the differences were merely a matter of artistic representation. He gently pointed out that Schiaparelli did not have any artistic training and had simply drawn things more definitely because he didn’t know how to represent the Martian surface naturalistically, or as it appeared. But Schiaparelli claimed that the cartographic differences stemmed from differences in observation. For his part, he gently suggested that Green did not have the same level of training in astronomical observation and therefore simply hadn’t perceived everything that Schiaparelli had seen through his telescope. [11]
Despite these discussions between Green and Schiaparelli about their maps’ differences, it was really up to the map viewers to settle the debate over which of the maps was most correct, meaningful, or useful. From that perspective, it is clear that Schiaparelli’s map won over both scientific and popular audiences. Although the historical record shows considerable controversy and even skepticism over the network of linear features (or canals, as they came to be called) on Schiaparelli’s map, astronomers almost immediately began working to confirm their existence.
From 1877 to 1884, Schiaparelli repeated his observations, confirming numerous linear features and adding new canals every two years. During that same time, no other major astronomer saw any linear features on the surface of Mars. Even so, it appears that most astronomers were actively trying to observe canals, indicating through their persistence that there was something fundamentally convincing about Schiaparelli’s map. In 1886, Schiaparelli’s «canals» were finally confirmed by independent observations in France and Belgium. [12] The two following decades were then marked by numerous canal observations and dramatic additions of detail to the Martian map. As the map changed and expanded, astronomers closely followed the authoritative standards Schiaparelli had set in 1878 for a geographically-based nomenclature and a definitive representation style.
The enduring influence of Schiaparelli’s Mars map stemmed partly from his own professional status (versus Green’s status as a highly respected amateur), but the visual authority of his map was a more important driver of his legitimacy as a Mars observer and interpreter. Schiaparelli’s map was drawn much more authoritatively than Green’s, making its claims nearly indisputable. The dark lines, sharp edges, definitive colors, and specific geographic labels visually implied that Schiaparelli was more certain than Green of what he saw.
