Mars is a station on Metra's Milwaukee District West Line in Chicago, Illinois. The station is 9.1 miles (14.6 km) away from Chicago Union Station, the eastern terminus of the line. In Metra's zone-based fare system, Mars is in zone 2. As of 2018, Mars is the 175th busiest of Metra's 236 non-downtown stations, with an average of 144 weekday boardings.