Under the Mars Surveyor '98 program, the Mars Climate Orbiter and Mars Polar Lander were the second set of spacecraft launched in NASA's long-term program of robotic exploration of Mars. The spacecraft was lost as it was entering orbit around Mars on September 23, 1999.
Materials here reveal facts, missions, and educational resources about Mars.
The Mars Observer spacecraft was to be the first U.S. spacecraft to study Mars since the Viking missions 18 years ago. The Mars Observer spacecraft fell silent just 3 days prior to entering orbit around Mars. Pathfinder deployed a small rover called Sojourner to explore the Martian landscape. Mars Fact Sheet - Learn the many differences between Earth and Mars in this geographical Fact Sheet on the Red Planet. The 1970's Viking mission did not return a Mars rock sample to Earth.