Mars Lander Team Applies for Mission Extension
An artist's conception of Phoenix, poised to dig into the Martian soil using its robotic arm.
Credit: SETI

NASA's Phoenix Mars Lander might be digging up the surface of the red planet for longer than expected. Mission controllers have requested an extension to the spacecraft's work on the planet's surface, has learned.

The $420 million mission has been investigating the dirt and ice of the northern reaches of Mars since it landed on May 25. The mission was slated to last for 90 sols, or Martian days (about 92 Earth days), ending at the end of August. Now it could be extended another 30 sols.

Because of the landing spot in the north polar region, the mission can't continue forever. Phoenix uses its two-wing solar array to convert sunlight into electricity to power its instruments, storing some power in a pair of rechargeable batteries. However, Phoenix's landing site is above Mars' Arctic Circle, so the sun isn't up during the whole Martian year and there eventually will be too little sunlight to power the instruments. (The sun is above the horizon all summer, then begins to set below the horizon come fall as it sets for the entire winter ? just as the sun does above the Arctic Circle on Earth.)

But with the success of the mission so far, and indications that Phoenix will be able to keep going until the arctic region plunges into the long darkness of winter, mission scientists want to keep going.

"We think that there's enough energy to continue digging and delivery to instruments through at least 120 sols, and then after that, our energy starts to go down, but we can still do operations as a weather station," said Phoenix robotic arm co-investigator Ray Arvidson of Washington University in St. Louis.

Dig this

Phoenix has been digging up samples of Martian dirt and the rock-hard ice layer that lies underneath for testing in its onboard instruments to determine their composition and look for signs that Mars may have been habitable at some point in its past.

If the team gets permission to extend the mission, they'll likely have at least another 30 days of digging, Arvidson told, adding that the team will "try to dig as long as we can and the resources permit."

Phoenix will also use it stereo camera, lidar instrument and other meteorological instruments to photograph the surface and make measurements of the Martian weather.

But these plans are "all predicated on permission to have an extended mission and finances, so that's all being negotiated right now with NASA headquarters," Arvidson said. He didn't know when NASA might decide whether or not to extend the mission.

The missions of NASA's Mars Exploration Rovers, Spirit and Opportunity, have also lasted longer than originally anticipated. The primary missions for each rover lasted for 90 days in 2003. The rovers are still trundling around the Martian surface more than four years later, thanks to dust storms that cleared dust off the vehicles' solar panels.

What about next year?

In November, Mars dips behind the sun and out of our view, but will eventually re-emerge. "Hopefully we'll still be alive after that," Arvidson said of Phoenix, so that the lander can continue making a few last measurements, if the extension plan is approved.

The setting Martian sun will gradually diminish the amount of energy available to Phoenix via its solar panels. ) As the sun sets and winter approaches, the temperature at Phoenix's landing site will start dropping and carbon dioxide ice will precipitate out of the atmosphere.

"As the seasons move from fall to winter on Mars ? it's something like 20 to 30 centimeters [about 8 to 12 inches] of CO2 ice forms out of the atmosphere," Arvidson said.

The colder winter temperatures and carbon dioxide ice accumulating on the spacecraft will ultimately spell its end, because the craft is not built to withstand these frigid conditions. Phoenix won't rise from the ashes when the sun comes up again in the Martian spring.

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