NEW YORK
—
Mission
controllers lost touch with the Mars Phoenix Lander Nov.
2, a
few weeks earlier than NASA had predicted.

“At this time we’re pretty convinced that the vehicle is no longer available for us to use,”
Phoenix
project manager Barry Goldstein of NASA’s Jet Propulsion Laboratory said during a Nov. 10 press briefing. “We knew this would eventually happen.”

NASA predicted in October that Phoenix likely would cease most science operations by mid-November and shut down completely sometime in December as fall and winter descends on Mars’ northern hemisphere, subjecting the solar-powered lander to nearly constant darkness.

Phoenix
transmitted its last signal Nov. 2, just over five months after making a May 25 landing near Mars’ north pole to study the arctic surface of the red planet.

During the course of its mission,
Phoenix
collected samples of martian dirt and subsurface water ice at its arctic landing site and analyzed them for signs of the planet’s past potential habitability.

Phoenix
successfully completed its primary mission by the end of August. Three months of extended operations pushed the total cost of the mission to $475 million.

“NASA’s gotten what they wanted out of this mission,” said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in
Washington
, though
Phoenix
‘s “demise is a little earlier than we’d hoped.”

Phoenix
‘s big finding was confirming the presence of water ice undersurface dirt in the northern plains.

It also found the dirt at the lander’s location was more alkaline than the soil the Mars Exploration Rovers, Spirit and
Opportunity
, sampled closer to the equator.
Phoenix
‘s measurements also unexpectedly turned up signs of perchlorate, a possible source of energy for any potential life that once could have graced the martian surface.

Phoenix’s science team now will begin to thoroughly analyze all the data received from the lander, said Phoenix Principal Investigator Peter Smith of the University of Arizona in Tucson, Ariz.

“
Phoenix
has given us some surprises, and I’m confident we will be pulling more gems from this trove of data for years to come,” Smith said.

The lander’s power supplies had been diminishing steadily in recent weeks as the sun dips toward the horizon with the approach of fall and winter.
Phoenix
went into its inactive safe mode briefly Oct. 28, when a dust storm obscured the sky and limited the amount of sunlight hitting the lander’s solar arrays.
Phoenix
restarted once the sun came up the following day, but continued to lose power at night then woke up again when sunlight hit its solar arrays the following morning.

The sequence of events that led to
Phoenix
shutting down were “exactly play-by-play what we anticipated doing,” Goldstein said, though they came about three weeks earlier than anticipated.
Mission
engineers had hoped to use the lander as a weather station at least through the end of November.

Although
Phoenix
has gone silent, the team will keep listening for signals from the spacecraft for a few more weeks. NASA also plans to listen in again in October 2009 when the sun finally will be high enough in the sky to generate enough energy to repower
Phoenix
, assuming the lander is not destroyed in the month ahead by extreme cold and carbon dioxide ice.

Though the team does not expect
Phoenix
to survive the winter, Goldstein said there is always the “hope that the vehicle will surprise us again.”