An astronomer named Percival Lowell founded this observatory in 1894. Here, astronomers studied Mars, searched for and discovered the planet Pluto in 1930, and pursued a variety of other types of research. Perhaps the most important discovery was made here in 1913 and 1914. Lowell Observatory astronomer, Vesto Slipher, trained the giant telescope on distant nebulae and found evidence that our universe is expanding. The work of many later scientists is based on this discovery.