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 The orbiting Odyssey satellite went into safe mode and failed to send instructions to Phoenix to claw into the permafrost to search for evidence of the building blocks of life, said Chad Edwards, chief telecommunications engineer at NASA's Jet Propulsion Laboratory in Pasadena.
It's the second time a relay problem has delayed the lander's schedule. The first glitch occurred two days after it landed, when another satellite, the Mars Reconnaissance Orbiter, turned off its radio.
Engineers worked to fix the problem with Odyssey, which will remain offline until Saturday, Edwards said. A preliminary investigation revealed the safe mode was probably triggered by high-energy particles from space interrupting the satellite's computer memory.
"The lander is fine," Edwards said.
Phoenix set down in Mars' northern latitudes to study whether the polar environment is capable of supporting primitive life. It communicates with Earth through Odyssey and the Reconnaissance Orbiter, which make daily passes over the lander to send commands and beam back images.
With Odyssey temporarily out of service, engineers told the Reconnaissance Orbiter to be the middleman between the lander and Earth.
Phoenix had planned to dig the first of three shallow pits north of where it landed and dump the dirt into a tiny oven, where it will be baked and studied this week. The earliest the lander can start the excavation will be Thursday, when new commands will be sent up.
The green light to scrape the Martian surface came after an extensive check of Phoenix's 8-foot robotic arm and other scientific instruments.
"It's absolutely an incredibly science-rich location," said chief scientist Peter Smith of the University of Arizona, Tucson, who heads the three-month, $420 million mission.
Before the actual work, Phoenix had playtime in the Martian dirt, doing two practice runs that involved scooping up and then dumping out fistfuls of soil. The tests yielded an intriguing scientific find: In both cases, the loose soil was mixed with white bits that scientists believe are either surface ice or salt deposits.
Phoenix zeroed in on three sites to the right of the test dig area that scientists have playfully named Baby Bear, Mama Bear and Papa Bear, after the "Goldilocks" fairy tale.
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 For the initial dig, scientists want the lander to cut into the Baby Bear site at an angle, dig three-tenths of an inch into the permafrost and drag the dirt into the arm's scoop like a backhoe.
Then Phoenix will swing its robotic arm 90 degrees and wait for further instructions to drop the scoopful of dirt into a miniature oven designed to heat the sample and analyze the vapors for traces of organic compounds, said Ashitey Trebi-Ollennu, a robotic arm engineer at the Jet Propulsion Laboratory.
Although the oven's spring-loaded doors did not fully open as scientists hoped, Smith said it should not be a problem. Over the next several days, Phoenix will scoop up soil from the other two sites for its microscope and wet chemistry lab to analyze.
Phoenix cannot detect fossils or living microbes. Instead, it will poke into the soil and ice to study whether liquid water ever existed and whether there are any organic compounds, those containing carbon and hydrogen atoms. Scientists generally agree that water, organics and a heat source are needed for a habitable environment.
Twin rovers that have been roaming near the Martian equator since 2004 have uncovered evidence that water once flowed at or near the surface of ancient Mars.
"We're just taking an exploratory step here," Smith said this week. "Our instruments are not designed to decode DNA molecules. ... We're looking for the basic ingredients that would allow life to prosper in this environment."
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On the Net:
Phoenix Mars: http://phoenix.lpl.arizona.edu/
[Associated
Press; By ALICIA CHANG]
Copyright 2008 The Associated
Press. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
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