Percival Lowell (1855-1916), US astronomer. Lowell's interest in astronomy was stimulated by Schiaparelli's report in 1877 of dark lines (canali) on Mars. Lowell believed there was intelligent life on Mars, a popular belief at the time. In 1894 he built an observatory in Arizona, USA. His most important contribution to astronomy was his prediction of the existence of a ninth planet outside the orbit of Neptune. Although Lowell searched for it from 1905 to 1914, it was not until 1930 that Pluto was found (by Tombaugh at the Lowell Observatory).