Use of this projection therefore implicitly introduced the idea that Mars was going to be understood in the same way as well-known sites of terrestrial navigation and exploration, like the tropical spheres of imperial expansion or of colonial settlement. The stereoscopic projection, on the other hand, mimicked the shape of earlier Mars sketches, thus relying on their perceived accuracy and objectivity. Furthermore, stereoscopic maps drew on popular excitement for new visual technologies, like the stereoscope, that promised to reveal new insights by offering visual access to phenomena that had previously been invisible to the naked or unaided eye. The emerging cartographic and visual formats of the Mars maps thus played a significant role in engendering popular interest in Mars, as well as influencing the nature of that interest. [8]
The Mapping Controversy of 1877-1878
The map of Mars was augmented throughout the nineteenth century as observational detail was added every time Mars made its biennial orbital lap past the Earth, sometimes passing close enough for excellent telescopic viewing. After decades of incremental cartographic development, a major mapping controversy then developed in the 1870s and 1880s, leading to major changes in scientific perspectives on Mars as well as to widespread popular belief in Martian canals and inhabitants. To understand these scientific and popular developments, it is critical to understand what was happening with the Martian map.
In the summer of 1877, Mars passed Earth very nearly at the point where the two planets’ elliptical orbits are closest to each other and also closest to the sun. This combination of Mars’s being extremely close to Earth and also highly illuminated offered an exciting opportunity for astronomer-cartographers to improve their maps of the red planet. After the planetary conjunction, two important maps became embroiled in controversy, one by the British astronomer Nathaniel Green and another by the Italian astronomer Giovanni Schiaparelli. Both of these maps capitalized on the opportunity to present incredible new geographic details for Mars, yet the two maps were so radically different that most astronomers felt the need to reject one of the maps in order to accept the other as correct. To understand how these maps differed in appearance and in their impact on map viewers, this section examines both the production and consumption of the Schiaparelli and Green maps.
Green, an English amateur who was a portrait artist and landscape painter by profession, left his London home and voyaged to the Portuguese island of Madeira to observe Mars during the summer of 1877. For two months, he observed Mars under good conditions and created 41 painstaking detailed color sketches of Mars.
