Update from SPACE.com:
posted: 20 June 2008 10:37 am ET
By Clara Moskowitz, Staff Writer
Despite recent glitches with NASA's Phoenix Mars Lander on the arctic plains of the red planet, the mission became a resounding success when it found signs of water ice on Thursday.
Four days ago Phoenix photographed dice-sized crumbs of bright material in a trench informally called "Dodo-Goldilocks." When the probe recently went back to look at the trench, they had vanished. The disappearing act convinced scientists the material was frozen water that vaporized after digging exposed it.
"It must be ice," said Phoenix principal investigator Peter Smith of the University of Arizona, Tucson. "These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice. There had been some question whether the bright material was salt. Salt can't do that."
The mission was designed to investigate whether the arctic plains environment could have been habitable to microscopic life. Water is an essential ingredient for life. Researchers knew there was abundant water ice at the polar caps, and there is strong evidence for water ice below the surface away from the poles, based on satellite observations. The Phoenix finding stands to be the first solid, photographic evidence for this subsurface ice away from the polar caps.Snow White
On Thursday the probe made another potentially exciting discovery: While digging in a different trench, called "Snow White 2," Phoenix's Robotic Arm connected with a hard surface that also may turn out to be an icy layer.
"We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench," said Ray Arvidson of Washington University in St. Louis, a co-investigator for the robotic arm.
The Phoenix science team spent Thursday analyzing the new images and data successfully returned from the lander earlier in the day.A rocky start?
Prior to the discovery, Phoenix had suffered a few glitches, including recent memory loss and a clogged oven. While these issues may give the mission the appearance of a rocky start, they are par for the course, mission managers said.
In fact, Phoenix has already been successful enough to merit a one-month extension to its planned 90-day mission.
Barry Goldstein, Phoenix project manager at NASA's Jet Propulsion Laboratory, said the spacecraft's troubles were the type of issues that could be expected for the complex $420 million dollar mission.
"We knew it was going to be difficult to operate on the surface of Mars, so we designed the mission such that we could guarantee that we'd meet our full mission success even if we lost one out of every three days on the surface," Goldstein told SPACE.com. "We're now on sol [Martian day] 24 and we've lost one. So by that metric we're way ahead of schedule."
Phoenix successfully landed in the flat Vastitas Borealis region of the Martian arctic on May 25 and subsequently deployed its robotic arm to begin scratching for frozen water ice beneath the dirt-covered surface.
But the probe lost some science data this week when its memory got clogged with housekeeping information regarding its computer functions. Engineers traced the problem to a pair of software bugs that caused the spacecraft's file-saving algorithm to run on an endless loop of robotic navel-gazing that created heaps of data — about 45,000 data packets when they normally expect only a few.
The glitch caused Phoenix to overwrite some science observations it had gathered the day before, though all this data was low priority and can be collected again. The issue also prevented mission managers from uploading Phoenix's science commands on Wednesday, the 23rd sol of the mission.
"The worst damage we had in all of this is we lost a sol on the surface — it's the first sol that we lost," Goldstein said. "We feel we have taken all the necessary steps to mitigate the problem. We won't have any overwritten science data anymore based on the corrective action we've taken."Early issues
Earlier in the mission, Phoenix encountered difficulty when trying to pour a sample of dirt into one of its instruments, the Thermal and Evolved-Gas Analyzer (TEGA) oven, which is designed to bake Martian dirt and analyze the vapors it emits to detect its composition.
When Phoenix's robotic arm first scooped dirt onto the oven's filter that sifts out coarse grains from fine, not enough of the stuff actual made it through into the instrument. But mission engineers fixed the problem by ordering Phoenix repeatedly use a vibration tool to shake the oven screen, jostling enough of a sample through the filter.
"The transfer into the TEGA was growing pains, in my opinion, in trying to learn how to get a sample into the oven. I expected we'd be struggling in learning how to get the samples delivered. Frankly, we resolved that very rapidly in my opinion and I'm very pleased," Goldstein said. "I was more concerned at the beginning when we had the problem with the short in the TEGA."
That first problem occurred just five days after the lander touched down on Mars. When Phoenix tried to start up the TEGA oven, one of the instrument's heating filaments short circuited. Luckily, the oven was able to function using a backup filament.
Overall, Goldstein said, the issues Phoenix has encountered have been the type of minor, but inevitable, setbacks one would expect with a complicated planetary mission.
"We're approximately one third into the mission and I believe it's going better than I'd expected," he said. "Not only am I pleased in the lack of quantity of glitches we've had, I'm also very pleased that the glitches we have had have really been very minor and we've been able to deal with them very quickly. It's a lot better than I expected and a lot better than we had planned for."
File comment: Sublimation of ice in the trench informally called "Dodo-Goldilocks" over the course of four days. Image credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University
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