Mars Observer — After a 17-year gap since its last mission to the red planet, the United States launched Mars Observer on September 25, 1992. The spacecraft was based on a commercial Earth-orbiting communications satellite that had been converted into an orbiter for Mars. The payload of science instruments was designed to study the geology, geophysics and climate of Mars.

The mission ended with disappointment on August 22, 1993, when contact was lost with the spacecraft shortly before it was to enter orbit around Mars. Science instruments from Mars Observer were reflown on two other orbiters, Mars Global Surveyor and 2001 Mars Odyssey.