Almost two years to the day after it landed on the red planet NASA has announced its Phoenix Mars Lander has officially ended operations after repeated attempts to contact the spacecraft were unsuccessful. Phoenix was not built to survive the dark, cold, icy winter on Mars and a new image transmitted by NASA’s Mars Reconnaissance Orbiter shows signs of severe ice damage to the lander’s solar panels.
Despite sending what turned out to be its last transmission on November 2, 2008, a little over five months after it landed on arctic plains in the north of Mars and two months after it completed its primary three month mission, NASA couldn’t eliminate the slim possibility that Phoenix had survived without listening for the lander after abundant sunshine had returned. The lander’s safe mode kept the option open to reestablish communications if it could recharge its batteries during the Martian spring.
Last week, NASA's Mars Odyssey orbiter flew over the Phoenix landing site 61 times during a final attempt to communicate with the lander. Unfortunately, no transmission from the lander was detected. Phoenix also did not communicate during 150 flights in three earlier listening campaigns this year.
An image of Phoenix taken this month by the High Resolution Imaging Science Experiment, or HiRISE, camera on board the Mars Reconnaissance Orbiter suggests the lander no longer casts shadows the way it did during its working lifetime.
"Before and after images are dramatically different," said Michael Mellon of the University of Colorado in Boulder, a science team member for both Phoenix and HiRISE. "The lander looks smaller, and only a portion of the difference can be explained by accumulation of dust on the lander, which makes its surfaces less distinguishable from surrounding ground."
Apparent changes in the shadows cast by the lander are consistent with predictions of how Phoenix could be damaged by harsh winter conditions. It was anticipated that the weight of a carbon-dioxide ice buildup could bend or break the lander's solar panels. Mellon calculated hundreds of pounds of ice probably coated the lander in mid-winter.
Even amongst the disappointment NASA is praising Phoenix’s achievements. “The Phoenix spacecraft succeeded in its investigations and exceeded its planned lifetime," said Fuk Li, manager of the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Although its work is finished, analysis of information from Phoenix's science activities will continue for some time to come."
During its mission, Phoenix confirmed and examined patches of the widespread deposits of underground water ice detected by Odyssey and identified a mineral called calcium carbonate that suggested occasional presence of thawed water. The lander also found soil chemistry with significant implications for life and observed falling snow. 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.
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