Most obituaries, such as the New York Times, 1/20/97 give more information than I ever knew about him. After his discovery of Pluto in 1930, he completed his formal education in astronomy, and continued to study minor planets in the solar system. He also predicted in 1950, that the surface of Mars would be covered with craters; which wasn't confirmed until 15 years later by the Mariner 4 flyby. Astronomers who work hard are rewarded with only one great discovery, and for Tombaugh, Pluto was 'it'.