After the Viking missions to Mars launched in the 1970s, NASA’s and the nation’s focus shifted elsewhere to the solar system. Two decades almost passed before another mission was set up, with a completely redesigned ship and all new scientific equipment. The Mars Global Surveyor would not land, but instead orbit around the planet between the north and south poles 12 times a day, taking continual snapshots of the same region that would help in the study of the planet’s atmosphere and climate changes.

On this day, September 11, in 1997, the Mars Global Surveyor began entering into orbit around Mars. To save on valuable fuel, the spacecraft used an innovative “aerobraking” maneuver, dipping into the Martian atmosphere to slow itself down and establishing an elliptical orbit.

Although NASA scientists were trying to stabilize the MGS in uncertain atmospheric conditions, their maneuver succeeded. The spacecraft entered into orbit and continued to transmit for nearly a decade, well ahead of its designed estimated operational limits. In one of the most important discoveries, the MGS transmitted data on small gullies. The discovery of debris flows on the planet’s surface might suggest the current presence of water.