Mars Lander Goes Inactive

NASA's Phoenix Mars Lander went into an inactive "safe mode" late Tuesday triggered by deteriorating weather conditions. The spacecraft also unexpectedly switched to its second set of redundant electronics and shut down one of its batteries.

As the Martian northern hemisphere, where Phoenix landed on May 25, transitions from summer to fall, the amount of sunlight available to the lander has dwindled and temperatures at Phoenix's landing site have been steadily dropping.

The spacecraft's declining health is no surprise to mission managers, who had planned way in advance for this seasonal change. Phoenix's primary mission ended in late August.

"This is a precarious time for Phoenix," said Phoenix Project Manager Barry Goldstein of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "We're in the bonus round of the extended mission, and we're aware that the end could come at any time. The engineering team is doing all it can to keep the spacecraft alive and collecting science, but at this point survivability depends on some factors out of our control, such as the weather and temperatures on Mars."

In recent days, temperatures have fallen significantly, dipping down overnight to minus 141 degrees Fahrenheit (minus 96 degrees Celsius) and only reaching minus 50 degrees Fahrenheit (minus 45 degrees Celsius) during the day, the lowest temperatures so far for the mission. This weather brought on a "low-power fault" on Phoenix, presumably a failure that the spacecraft detected and responded to by entering its power-saving safe mode.

To make matters worse, a mild dust storm blowing through Phoenix's north polar landing site, along with accumulating water-ice clouds in the atmosphere, has reduced the amount of sunlight reaching the spacecraft, further hindering recent attempts to keep it up and running for as long as possible.

Phoenix has been operating in the Martian arctic for more than five months, digging up samples of dirt and rock-hard subsurface water ice and analyzing them for signs of past potential habitability. Phoenix finished gathering its remaining samples last week.

All of the lander's science activities have been put on hold for the next several days to allow the spacecraft to recharge and conserve power. Mission controllers won't try to resume normal operations before the weekend.

The ability to communicate with the lander has not been affected, but the team decided to cancel communication sessions on Wednesday morning in order to conserve power.

On Tuesday, the mission announced plans to turn off four of the spacecraft's heaters, one at a time, to conserve power for the remainder of the mission. The low-power faults late on Tuesday prompted engineers to shut down two heaters instead of one as originally planned.

One of those heaters warmed the electronics for Phoenix's robotic arm, robotic-arm camera, and Thermal and Evolved-Gas Analyzer (TEGA), which bakes samples and analyzes the vapors given off to determine the samples' composition. The second heater served the lander's pyrotechnic initiation unit, which hasn't been used since landing.

Mission controllers hope that switching off the two heaters will preserve enough power to keep the lander's camera and meteorological instruments running.

The engineering team anticipates that Phoenix will essentially serve as a meteorological station once its power supplies dip enough that most instruments can no longer be run and kept within their optimal temperature range. Mission planners previously predicted that Phoenix would no longer have enough power for any operations by the end of November/beginning of December. But just when the lander will truly die is uncertain.

"It could be a matter of days, or weeks, before the daily power generated by Phoenix is less than needed to operate the spacecraft," said JPL mission manager Chris Lewicki. "We have only a few options left to reduce the energy usage."

• Video - Phoenix: Digging on Mars
• Special Report: Phoenix Mars Lander
• Images: Phoenix on Mars!