The Mars Global Surveyor was launched on November 7, 1996. At its time, it was the first successful mission to Mars in two decades. The Mars Global Surveyor arrived at Mars on September 12, 1997. It spent a year and a half changing its orbit from a looping eclipse to a circular track. Then, the spacecraft began its mission in March 1999.
The Mars Global Surveyor's purpose was to study the surface and atmosphere of Mars. One of its main discoveries was that it saw that Mars had repeatable weather patterns. The Surveyor also took pictures of Mars' surface which documented gullies, suggesting that water could have possibly been on the surface of Mars at some point.
The discoveries of the Mars Global Surveyor changed the beliefs of scientists about the surface of Mars. Many studies afterward were done about water on the surface of Mars, which led to NASA confirming that current evidence leads to water flowing on today's Mars. The Mars Orbital Camera, which was the camera used on the Surveyor, was used in 2006 to provide guidance to the aerobraking maneuvers of the Mars Reconnaissance Orbiter. The photos taken by the Surveyor were used to find acceptable landing spots for the Phoenix and Mars Science Laboratory in 2007 and 2009, respectively.