Mars Global Surveyor, 1996.
© National Aeronautics & Space Administration / Science & Society
Mars Global Surveyor was launched by NASA in 1996 and entered orbit around Mars in September 1997. Its main objective was to map the entire planet. After arriving, the spacecraft carried out various manoeuvres to alter its orbit from a highly elliptical two-hour circular polar orbit which allowed it to cover the entire planet every seven days. As well as producing high resolution images showing the Martian surface in unprecedented detail, the Mars Global Surveyor has greatly expanded our knowledge of the topography and gravity, weather and climate, surface and atmospheric composition, and magnetic field of the red planet.