Percival Lowell, American astronomer and mathematician (died 1916)

Percival Lowell was an American businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, and furthered theories of a ninth planet within the Solar System. He founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death.

March 13 is the 72nd day of the year in the Gregorian calendar; 293 days remain until the end of the year.