Mars - Mars Global Surveyor

More than twenty years passed between the launch of the highly productive Viking missions and another successful mission to Mars. In November 1996 the Mars Global Surveyor took off from Cape Canaveral, Florida, atop a Delta II rocket. The spacecraft arrived near the planet ten months later. To save on fuel the Global Surveyor was put into its final Martian orbit very slowly through a process called aerobraking.

During aerobraking a spacecraft is repeatedly skimmed through the thin upper atmosphere surrounding a planet. Each skim reduces the speed of the craft due to frictional drag. Aerobraking eliminates the need for extra fuel to do a retro-burn to slow down a spacecraft.

The Global Surveyor was put through a very long series of gentle skims for a year and a half. Generally aerobraking does not take this long. Flight controllers were extremely careful with the Surveyor, because one of its solar panels did not fully deploy during flight. Scientists were afraid that aggressive skimming might put too much stress on the panel.

In March 1999 the spacecraft began its mapping mission. This continued for one Martian year (687 days). The most significant finding during mapping was images of gullies and other flow features that scientists believe may have been formed by flowing water. Surveyor also captured close-up photographs of Mars's moon Phobos. The images reveal that the moon is covered with at least three feet of powdery material.

In April 2002 Global Surveyor began performing data relay and imaging services for other NASA spacecraft carrying out missions at Mars. As of 2006 Surveyor was still in orbit and functioning properly.