You will be given a definition of a task first, then some input of the task.
Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.

NASA 's Mars Exploration Rover ( MER ) mission is an ongoing robotic space mission involving two Mars rovers , Spirit and Opportunity , exploring the planet Mars . It began in 2003 with the launch of the two rovers : MER - A Spirit and MER - B Opportunity -- to explore the Martian surface and geology ; both landed on Mars at separate locations in January 2004 . Both rovers far outlived their planned missions of 90 Martian solar days : MER - A Spirit was active until 2010 , while MER - B Opportunity is still active in 2018 , and holds the record for the longest distance driven by any off - Earth wheeled vehicle .
Output:
Mars Exploration Rover