The planet Mars, 1880.

UNITED KINGDOM - JUNE 12: Illustrated plate from 'Astronomie Populaire - Description Generale du Ciel', by the French astronomer Camille Flammarion (1842-1925), depicting a map of Mars showing continents and oceans). In this, his best-selling epic work, Flammarion speculated that Mars was 'an earth almost similar to ours [with] water, air, showers, brooks and fountains. This is certainly a place little different from that which we inhabit'. The Italian astronomer Giovanni Schiparelli reported that he had observed �canali� (channels) on Mars in 1877. This sparked a surge of interest in the possibility that Mars might be inhabited. Closer examination of Mars in the 20th century gradually proved that it was a dry world with only a very thin atmosphere, and any life was very unlikely to exist. (Photo by SSPL/Getty Images)