Mars is a borough in Butler County, Pennsylvania, USA. The population was 1,746 at the 2000 census. According to the United States Census Bureau, the borough has a total area of 0.4square miles (1.0Square kilometers), all of it land. The borough of Mars was founded in 1873, and is situated about halfway between the cities of Pittsburgh and Butler. The small community is nestled in a small valley along Breakneck Creek with PA 228 located about a mile south of Mars, and the Mars-Evans City Road located to the north. It is home to the popular roadside attraction, the Mars "Spaceship" or "Flying Saucer".