The Mars Polar Lander, also known as the Mars Surveyor '98 Lander, was a robotic spacecraft lander launched by NASA on January 3, 1999, to study the soil and climate of Planum Australe, a region near the south pole on Mars. It formed part of the Mars Surveyor '98 mission. The launch mass of the spacecraft is approximately 583 kg, including 64 kg of fuel, an 82 kg cruise stage, a 140 kg aeroshell/heatshield, and the two 3.5 kg microprobes.

On December 3, 1999, however, after the descent phase was expected to be complete, the lander failed to reestablish communication with Earth. A post-mortem analysis determined the most likely cause of the mishap was the premature termination of the engine firing prior to the lander touching the surface, causing it to strike the planet at a high velocity.