Lowell (Martian crater) Lowell (Martian crater) The Lowell Crater is a large impact crater on Aonia Terra in the Thaumasia quadrangle of Mars. The crater is about 203 kilometers (127 miles) in diameter. Lowell Crater has a ring of mountains on its floor which gives it a sort of bull's eye appearance. Its nearby features include the craters Slipher to the north, Douglass to the east, and Coblentz to the southwest, the small mountain Aonia Mons to the west, and Aonia Planum to the southeast. Lowell Crater is named for Percival Lowell who built the Lowell Observatory in Flagstaff, Arizona, in 1894, and
Percival Lowell Planet X. Lowell started a search program in 1906 using a camera in aperture. The small field of view of the reflecting telescope rendered the instrument impractical for searching. From 1914 to 1916, a telescope on loan from Sproul Observatory was used to search for Planet X. Lowell did not discover Pluto but later Lowell Observatory (observatory code 690) would photograph Pluto in March and April 1915, without realizing at the time that it was not a star. In 1930 Clyde Tombaugh, working at the Lowell Observatory, discovered Pluto near the location expected for Planet X. Partly in recognition of