Martian winter frost ices Phoenix lander mission

NASA's Phoenix Mars Lander mission is officially over, thanks to sharp pictures from a Mars-orbiting camera operated by the University of Arizona that appear to show the collapse of the lander's solar panels due to an expected coating of heavy winter frost.

The Phoenix lander fulfilled all of its major scientific goals during a three-month prime mission and two months of extended work following its landing in the north polar region of the red planet on May 25, 2008.

In a first for NASA planetary exploration, the landed portion of the mission was directed from an operations center in Tucson at 6th Avenue and Drachman Street, rather than from a NASA field center.

The solar-powered lander was not designed to survive the dark, harsh polar winter on Mars. Nevertheless, NASA's Mars Odyssey orbiter flew over the Phoenix landing site 61 times last week in a final attempt to communicate with it. No return signal was detected then, nor in 150 over flights during three other listening campaigns earlier this year.

In an image taken this month from orbit by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissance Orbiter mission, the desk-sized lander looks significantly smaller than it did during its operational life, and it casts a less distinct shadow.

"The latest HiRISE image appears to show that a solar panel of the Phoenix lander has collapsed," said University of Arizona planetary scientist Alfred McEwen, the principal investigator for the HiRISE project.

The carbon dioxide gas that accounts for 95 percent of the composition of the Martian atmosphere annually forms a blanket of wintertime frost at least a foot thick in the region where Phoenix landed, according to McEwen.

This heavy load of ice is more than the relatively fragile solar panels, which deployed like umbrellas after landing, were designed to support.

Meanwhile, scientists continue to poor over the five months of data returned by Phoenix to tease out further knowledge about the complex layered landscape where the lander settled two Earth years ago.

During its mission, Phoenix confirmed and examined patches of the widespread deposits of underground water ice detected by Odyssey, and identified a mineral, calcium carbonate, which suggests that thawed liquid water has occasionally been present at the site.

The suite of instruments on the lander's deck also observed falling snow, and conducted chemistry experiments on the soil that found intriguing implications for the possible existence of life on Mars.

The mission's biggest surprise was the discovery of perchlorate, an oxidizing chemical on Earth that is food for some microbes and potentially toxic for others.

"We found that the soil above the ice can act like a sponge, with perchlorate scavenging water from the atmosphere and holding on to it," said Peter Smith, Phoenix principal investigator at the UA. "You can have a thin film layer of water capable of being a habitable environment. A micro-world at the scale of grains of soil - that's where the action is."

The perchlorate results have triggered follow-up research as scientists investigate the implications of its antifreeze properties and its astrobiological potential as an energy source for microbes.

Discovery of the ice in the uppermost soil by Odyssey pointed the way for Phoenix. More recently, the MRO detected numerous ice deposits in middle latitudes at greater depth using radar and exposed on the surface by fresh impact craters.

"Ice-rich environments are an even bigger part of the planet than we thought," Smith said in a statement. "We are finding that a complex chemistry associated with the icy soil makes this vast region an excellent destination for future missions searching for Martian life."

MRO reached the planet in 2006 to begin a two-year primary science mission that has subsequently returned more data than all previous Mars missions combined. Its data show Mars had diverse wet environments at many locations for differing durations during the planet's history, and that climate-change cycles persist in the present era.

The Phoenix mission was led by Smith at the UA, with project management by NASA's Jet Propulsion Laboratory and a development partnership at Lockheed Martin in Denver. The UA operates the HiRISE camera, which was built by Ball Aerospace and Technologies Corp. in Boulder, CO.