Late 19th century possibility of life on Mars

• Astronomy borrowed representational tools from geography (e.g. mapmaking, travelogues)
• Images of geometrical lines in the landscape implied canals to some people
• There was considerable discussion of this debate in the popular press
• Life on Mars, plurality of worlds thesis
• Information about Mars was conveyed through maps
• Astronomers and techniques from geography: travel narratives, explorer accounts and geographic expeditions
• “Earthlike” picture of Mars, geographically educated public
• Maps of Mars allowed planet to be thought of geographically, it created territorial competition amongst astronomers (to name, map areas), and enhanced the belief in artificial canals
• 1877 Mars in opposition to the Earth, observations of planet made
• Green’s soft shading versus Schiaparelli’s hard lines, suggest islands and thus water and potentially canals
• General features were in agreement
• Green’s map borrowed from observations by other astronomers, Schiaparelli’s was based on his own, extensive observations
• Observations made at clear locations, telescopes were good, work connected to previous observations, Green’s maps integrated earlier observations
• Schiaparelli’s maps were more influential, with most astronomers adopting his nomenclature and artistic style
• His representation was clear and familiar
• Schiaparelli well known and respected for astronomical work
• Schiparelli’s names contested, didn’t use astronomer’s names, but names from classical geography and mythology (Arabia, Atlantis, Libya and Zephyria)
• Confirmations of the Martian canals, new sightings of more canals
• Larger telescopes did not reveal canals, Mars canal advocates argued that location of the observation mattered more
• Equatorial sites, islands and mountains, remote locations
• Direct observation from a privileged location, size of the telescope and the authority of the observer
• Cold Mars thesis, size and distance from the sun, melting ice caps
• Darker areas as seas, no polarized light or glint from the water’s surface, dark areas could be plants
• Astronomers also used comparisons with Earth features
• Mars was representative of what Earth would be like in the future, cold and dry and desertlike
• Martian canals so long and large, result of an advanced civilization