Mars lander succumbs to winter

12:12, 11 November 2008
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The Phoenix Mars lander is dead

The Phoenix Mars lander is dead.

Mission managers said Monday that they had not heard from the NASA spacecraft for a week and that they thought it had probably fallen quiet for good.

“At this time, we’re pretty convinced that the vehicle is no longer available for us to use,” said Barry Goldstein, the project manager. “We’re actually ceasing operations, declaring an end to mission operations at this point.”

With the onset of winter and declining power generated by the Phoenix’s solar panels, managers knew the lander would succumb soon, but had hoped to squeeze out a few more weeks of weather data.

But on Oct. 27, just after Phoenix finished its last major experiment analyzing Martian soil, an unexpected dust storm hit. The batteries, already low from running the experiment, ran out of energy.

The spacecraft first put itself into a low-energy “safe mode,” then fell silent. It revived itself on Oct. 30, but, with the dust still swirling, was never able to fully recharge its batteries. Each day, the solar panels would generate enough electricity for the spacecraft to wake up, but then the batteries drained again.

The last communication came on Nov. 2. Mr. Goldstein said the orbiting spacecraft would continue to listen for a few more weeks on the faint chance that the Phoenix defies their expectations.

The Phoenix landed in May to examine the northern arctic plains, and the $428 million mission, originally scheduled to last three months, was extended twice

“I’m just thrilled to death what we’ve been able to do here,” said Peter H. Smith of the University of Arizona, the mission’s principal investigator. The spacecraft accomplished all of its main objectives, but some science remained unfinished. The Martian soil proved to be extremely clumpy, and the spacecraft had recurrent trouble getting the samples through gratings into the spacecraft’s laboratory apparatus.

Dr. Smith admitted disappointment that a sample from one of the trenches that the Phoenix had dug was never successfully analyzed. “We got it all the way up to the instrument and even tried pressing it down,” Dr. Smith said. “But it wouldn’t go in.”

But Dr. Smith highlighted what the Phoenix did discover. It confirmed a layer of ice not far below the surface. It found some carbonates and clays, which suggest that liquid water may have be present within the past few millennia. It found the arctic soil to be alkaline, not acidic as has been observed in other parts of Mars. It also discovered perchlorates, a class of chemicals that in high concentrations can be toxic to life, but which can also serve as a food source for some microbes.The spacecraft took 25,000 photographs, including panoramas of the landing and microscopic images of dust particles.

“It’s really an Irish wake, not a funeral that we’re looking forward to,” said Douglas McCuiston, director of the Mars Exploration Program at NASA headquarters. “NASA got what it wanted out of this mission.”

The data may yet reveal the presence of carbon-based molecules that could be building blocks for life, Dr. Smith said, and that the region might, at least occasionally, be suitable for life. The Phoenix was not designed to look directly for signs of life. Dr. Smith said the scientists had begun writing the scientific articles describing their findings.

In the coming months, when sunlight disappears entirely in the northern plains, temperatures will fall to minus-240 to minus-300 degrees Fahrenheit, and the Phoenix will become encased within carbon dioxide ice. When spring returns, NASA plans to try reviving the Phoenix again, but the expectation is that the spacecraft’s electronics will not survive the long, deep freeze.

The New York Times

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