Spacecraft lander on Mars.

Artist's concept of Mars Polar Lander on the surface of Mars. Credit: NASA/Jet Propulsion Laboratory-Caltech

Mars Polar Lander and Deep Space 2 were to make the first in depth exploration of the carbon dioxide ice cap on the Martian south pole, but the lander and both Deep Space 2 impact probes were lost after an unsucccessful landing.

  • A mishap investigation found a sensor malfunction caused Polar Lander's engines to cut off too soon. All three probes crashed on the surface.
  • The Deep Space 2 probes were nicknamed Amundsen and Scott after the famed human explorers who led expeditions to Earth's South Pole.
  • The Phoenix lander, which arrived on Mars in 2008, eventually completed most of Mars Polar Lander's objectives.
Launch Date Jan. 3, 1999 | 20:21:10 UT
Launch Site Cape Canaveral Air Force Station / Launch Complex 17B
Launch Vehicle Delta 7425-9.5 (no. D265)
Science Target Mars
Status Unsuccessful
Agency NASA
Alternate Names Mars Surveyor '98 Lander, MPL, 25606, NSSDCA/COSPAR ID: 1999-001A

Key Dates

Jan. 3, 1999 | 20:21:10 UT: Launch

Dec. 3, 1999: Mars Arrival

Dec. 16, 1999: Missions Declared Lost

In Depth

The Mars Polar Lander (MPL) was one of NASA’s Mars Surveyor missions that called for a series of small, low-cost spacecraft for sustained exploration of Mars.

MPL’s primary goal was to deploy a lander and two penetrators (known as Deep Space 2) on the surface of Mars to extend our knowledge on the planet’s past and present water resources. The objective was to explore the never-before studied carbon dioxide ice cap, about 1,000 kilometers from the south pole. The mission also called for recording local meteorological conditions, analyzing samples of polar deposits, and taking multi-spectral images of local areas. MPL was to have performed its mission simultaneously with that of the Mars Climate Orbiter that would have acted as a communications relay during its surface operations.

Artists concept of Deep Space 2
Artist's concept of Deep Space 2. Credit: NASA/Jet Propulsion Laboratory-Caltech

MPL itself comprised a bus section (for power, propulsion, and communications during the outbound voyage) and a 639-pound (290-kilogram) lander that stood 3.5 feet (1.06 meters) tall on the ground. The lander was equipped with a 6.6-foot (2-meter) long remote arm to dig into the terrain and investigate the properties of Martian soil (using the Thermal and Evolved Gas Analyzer).

Having arrived at Mars on Dec. 3, 1999, the spacecraft would enter the atmosphere, and about 10 minutes prior to landing, would jettison its cruise stage and solar panels and then release the two 7.9 pound (3.572 kilogram) (each) Deep Space 2 microprobes. Unlike Mars Pathfinder, MPL was scheduled to make a completely controlled landing using retrorockets all the way to the surface. Landing was scheduled for 21:03 UT on Dec. 3, 1999 with two-way communications planned to begin 20 minutes later.

The two Deep Space 2 microprobes (renamed Amundsen and Scott on 15 November 1999), meanwhile, would impact the ground at a speed of 447 ph (200 meters/second) about 50–85 seconds prior to the lander and about 62 miles (100 kilometers) away. Each penetrator was designed to obtain a small sample of subsurface soil using an electric drill for analysis. The microprobes’ mission was expected to last about 36 hours while the lander mission would continue until March 1, 2000.

Mars Polar Lander successfully left Earth on a Mars transfer trajectory on Jan. 3, 1999. During its traverse to Mars, the spacecraft was stowed inside an aeroshell capsule. The complete vehicle approached Mars in early December in apparently good health.

Last contact with the vehicle was at 20:02 UT on Dec. 3, 1999 as the spacecraft slewed to entry attitude. Then, traveling at 37,804 mph (6.9 kilometers/second), the capsule entered the Martian atmosphere about 8 minutes later. Controllers expected to reestablish contact 24 minutes after landing (scheduled for 20:14 UT) but no signal was received. With no communications for over two weeks, on Dec. 16, 1999, NASA used the Mars Global Surveyor orbiting Mars to look for signs of the lander on the Martian surface, but the search proved fruitless. On Jan. 17, 2000, NASA finally terminated all attempts to establish contact with the lost lander.

An independent investigation into the failure, whose results were released publicly on March 28, 2000, indicated that the most probable cause of the failure was the generation of spurious signals when the lander’s legs deployed during the descent. These signals falsely indicated that the spacecraft had touched down on Mars when in fact it was still descending. The main engines prematurely shut down, and the lander fell to the Martian landscape.

The Phoenix lander, which arrived on Mars in 2008, subsequently accomplished most of the original Mars Polar Lander’s objectives.

Additional Resources


Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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