American astronomer Percival Lowell was born in Boston of a patrician New England family. His sister was the noted poet Amy Lowell. Educated at Harvard University, he established an observatory in Arizona in 1894 (known now as Lowell Observatory). Lowell is best known, however, for his observations of Mars. His advocacy of the presence of intelligent life on Mars had a considerable impact on astronomy during the early twentieth century. Mars is the only planet in the solar system whose surface is directly visible from earth. Lowell and others spent many long nights peering through telescopes at the planet, and they interpreted the random pattern of light and dark areas as a network of dark… lines girdling the red planet. These long dark lines turned out to be optical illusions, as was shown by a number of American spacecraft that took close-up photographs of the planet during the 1960's and 1970's. Lowell, however, was a vocal proponent of the idea that these lines were a network of globe-girdling canals, and the clear implication was that the planet harbored a species of intelligent beings. Although public interest was galvanized by Lowell's discoveries and by his popular books, the astronomy community was less receptive to his ideas. Lowell was also known for his prediction of the existence of a ninth planet in the solar system. That planet, Pluto, was discovered by Clyde Tombaugh in 1930.