Mars Polar Lander

Agency

NASA

Launched

1999-01-03

Landed

Never landed

Mass

290 kg

Technical Details

Agency	NASA
Country	🇺🇸 USA
Landing Site	South polar region (~75°S) — never reached
Power System	Solar panels
Mass	290 kg

Key Findings

1.Never achieved surface operations — lost during entry, descent, and landing at the Martian south polar region on December 3, 1999
2.Likely failure cause: premature thruster shutdown triggered by false vibration signal from landing legs deploying ~40 m above the surface
3.Carried two Deep Space 2 microprobes (also lost) designed to impact and penetrate the polar soil
4.Part of the Mars Surveyor 1998 programme — twin failure alongside Mars Climate Orbiter drove sweeping NASA review of processes and oversight
5.Loss prompted the establishment of NASA's Mars Exploration Program Standing Review Board and independent mission reviews

Mission Outcome

Mars Polar Lander was lost during its December 3, 1999 entry, descent, and landing sequence, never returning surface data. The most probable cause was a software flaw that interpreted vibration from landing-leg deployment as touchdown, causing the descent engines to shut off roughly 40 metres above the surface. Together with the earlier loss of Mars Climate Orbiter, the failure catalysed fundamental changes to NASA's planetary mission development and review processes.

Sources

[1] NASA NSSDCA — retrieved 2026-06-01

← All Mars Landers