How NASA’s Phoenix will land on Mars

By Jeremy Hsu

updated 1:21 p.m. ET May 14, 2008

NASA's Phoenix Mars Lander aims to not flame out when it descends to the arctic surface of the Red Planet in less than two weeks.

The new Martian probe will try to avoid the fate of its crashed predecessor, NASA's Mars Polar Lander, when deploying a parachute and braking rockets to slow its plunge and make a successful three-point landing.

"This is not a trip to grandma's house," said Ed Weiler, associate administrator of NASA's Science Mission Directorate at the agency's headquarters in Washington, D.C. "Putting a spacecraft safely on Mars is hard and risky."

Phoenix managers refer to the probe's descent as "seven minutes of terror" that will define the future of the spacecraft's $420-million mission. The robotic arm-equipped spacecraft is due to land near the Martian north pole on May 25 to study nearby water ice and determine if the region was once habitable for primitive life.

"Hopefully the outcome will be different from the Mars Polar Lander outcome," said Rob Grover, NASA engineer at the Jet Propulsion Laboratory in Pasadena, Calif.

Mars Polar Lander entered the Martian atmosphere near the planet's south pole in 1999, but a software glitch caused a premature shutdown of the spacecraft's engines. It crashed while falling at 50 mph instead of making a soft landing. NASA has worked since then to ensure Phoenix doesn't suffer the same fate.

"The No. 1 cause was the faulty indicator on touchdown sensor," Grover told SPACE.com, adding that the sensor falsely told the Mars Polar Lander that it had already landed.

Engineers have since corrected the software issue and made the overall system more robust to avoid future errors.

"We feel like we have adequately tested this vehicle," Phoenix project manager Barry Goldstein said in a Tuesday mission briefing, but added that there is always room for the unexpected. "We fire 26 pyrotechnic events in the last 14 minutes of this vehicle, and every one of those has to go off as planned ... We're very hopeful for success on the 25th."

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