NASA's Phoenix Mars lander, subjected to extreme low temperatures and crippling ice buildups it was never designed to endure, apparently suffered severe damage during the Martian winter that ended any chance of additional science operations, officials said Monday.
Designed to operate for just three months, Phoenix exceeded expectations, beaming back a steady stream of scientific data for five months before waning sunlight and the approaching Martian winter prevented its solar arrays from generating enough power to keep the craft warm and electronically conscious.
Engineers did not believe the lander could survive a northern latitude winter on Mars, but the spacecraft was programmed to attempt contact if it ever warmed up and received enough sunlight to come out of electronic hibernation. As winter faded into spring at the Phoenix landing site, engineers listened for signs of life during fly-overs by NASA's Mars Odyssey orbiter.
But during 61 fly-overs last week, and more than 150 earlier attempts, nothing was heard. And a photograph of the lander snapped by NASA's Mars Reconnaissance Orbiter earlier this month showed what engineers interpreted as severe ice damage.
Comparing before-and-after images, it appears one or both of the lander's two fan-like solar panels may have broken off or collapsed under the weight of wintertime carbon dioxide ice buildups.
"Now we know," said Project Manager Barry Goldstein in a telephone interview from the Jet Propulsion Laboratory. "I was never optimistic whatsoever and never really held out any hope, quite frankly. As a matter of fact, what's most interesting is that our postulated failure mode has been somewhat verified by those images. We had speculated that the first thing to go would be the solar arrays. We expected the ice to build up on the solar arrays themselves and to collapse under the pressure.
"Anyway, we had expected this to happen," he said. "In all likelihood, that was not the only thing that would have caused the vehicle to fail, but at least we have some visual evidence that supports the lack of communication."
In the Mars Reconnaissance Orbiter images, "before-and-after images are dramatically different," Michael Mellon, a science team member at the university of Colorado, said in a NASA statement. "The lander looks smaller, and only a portion of the difference can be explained by accumulation of dust on the lander."
Comparing the sizes of shadows cast by Phoenix in the before-and-after photos, it appears the solar arrays may no longer be attached. In any case, no additional attempts to contact the spacecraft will be made.
Phoenix landed on Mars May 25, 2008, making a powered descent to the surface. Unlike the Mars rovers Spirit and Opportunity, which landed on opposite sides of the planet near the Martian equator, Phoenix set down in the extreme northern latitudes to search for signs of hidden water ice.
Over the next five months, Phoenix used a robot arm to scoop up soil samples, subjecting the material to a battery of sophisticated tests. Along with confirming the existence of subsurface ice, Phoenix identified calcium carbonate, a chemical indicating the occasional presence of liquid water, and perchlorate, "an oxidizing chemical on Earth that is food for some microbes and potentially toxic for others," NASA said in a release.
"From the program point of view, clearly this was groundbreaking, both literally and figuratively, in that we were able to get verification for the first time of subsurface water on Mars as opposed to just CO2, which we knew was there, and obviously the discovery of perchlorate and other things," Goldstein said.
Phoenix followed in the footsteps of the ill-fated Mars Polar Lander, which disappeared during final approach to Mars in 1999.
"From a personal point of view it was a vindication," Goldstein said of Phoenix. "We put an enormous amount of effort on this mission to really vindicate the failed Polar Lander mission...It basically says when you put the right people on the job, you can accomplish almost anything."