The Mars Surveyor 2001 project was a multi-part Mars exploration mission intended as a follow-up to Mars Surveyor '98. After the two probes of the 1998 project, Mars Climate Orbiter and Mars Polar Lander, were both lost, NASA's "better, faster, cheaper" exploration philosophy was re-evaluated, with a particular eye on the two 2001 project probes. As a result, the mission, along with the launch of its lander and rover, were canceled in May 2000, but the decision was made to continue development with its orbiter counterpart. The orbiter launched as 2001 Mars Odyssey in April 2001, in a mission independent of the Mars Surveyor project, and reached Mars in October 2001. After being placed in a cleanroom in 2001 and stored since, the nearly-completed lander component was eventually reused to fly the Phoenix mission, which launched in August 2007 and landed successfully on Mars in May 2008.

The Mars Polar Lander, also known as the Mars Surveyor '98 Lander, was a 290-kilogram 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. 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 premature termination of the engine firing prior to the lander touching the surface, causing it to strike the planet at a high velocity.