Lowell was an astronomer who built a private observatory in Arizona to study Mars and championed the idea that intelligent inhabitants of the Red Planet had constructed a planetwide system of irrigation there. He believed that the so-called canals of Mars were bands of cultivated vegetation dependent on this irrigation. His theory, long vigorously opposed, was finally put to rest by images taken by the US Mariner spacecrafts. Lowell did, however, correctly predict the existence of what “planet”? Discuss