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Phoenix set for the big dig

The craft is to gouge Mars' surface, testing water and soil samples at a site scientists have dubbed Holy Cow.

June 03, 2008|John Johnson Jr. | Times Staff Writer

After troubleshooting an electrical problem on NASA's Phoenix lander and performing a test scoop into the crumbly surface of the Martian northern plain, scientists said Monday that they are ready to dig for ice as early as today.

Phoenix is the first spacecraft designed to taste the water on an alien planet.

Over the weekend, it sent back images showing white streaks under the lander that could be surface ice. Scientists were so excited that they nicknamed the site Holy Cow.

"It's a thrill for me to find out we're in a really great place to do the science we want to do," said Peter Smith of the University of Arizona, the lead scientist on the $420-million mission.

Even if the patches turn out to be a more common salt, scientists are certain large stores of ice lie inches beneath the lander.

Phoenix, which arrived May 25 on Mars, is managed by the Jet Propulsion Laboratory in La Canada Flintridge.

Scientists tested Phoenix's nearly 8-foot-long robotic arm by extending it to the ground, leaving an imprint that researchers dubbed Yeti because it resembles a large Abominable Snowman-style footprint. The arm also scooped up a bit of soil.

"The soil is crumbly," said Raymond E. Arvidson of Washington University in St. Louis during a briefing from Tucson on Monday morning. "It's kind of like cemented garden soil."

He said the robotic arm should not have any trouble digging into the soil: "When you push on it, it breaks apart. It's not going to be really strong stuff."

The real excavation work is to begin as early as today. Scientists are targeting three sites adjacent to the lander that they have dubbed Baby Bear, Mama Bear and Papa Bear.

Each soil sample will undergo four days of testing, with the lander's instruments heating the samples to ever-higher temperatures and measuring the vapors to identify the constituents. The science team is primarily looking for organic compounds, those containing carbon and hydrogen.

"The robotic team is ready to get on with business," Arvidson said.

A potentially serious problem with one of the main instruments, the Thermal and Evolved Gas Analyzer, or TEGA, cropped up several days ago: an electrical short on a filament that uses a magnetic field to charge particles for analysis in Phoenix's mass spectrometer. Without this instrument, Phoenix could have been crippled before it started its work.

"It was a bit of a scare," Smith said. He speculated that a soil particle contaminated the filament to cause the short.

Engineers switched to a backup. "It was successful," Smith said. "TEGA is ready to go and perform the science on the soil. We're pretty excited to get on with business."

If the white patches under the lander are not ice, they probably will turn out to be a kind of salt called kieserite.

NASA's two Viking missions that landed in 1976 turned up kieserite, which is often left by the evaporation of thin films of water. The finding was one of several that led scientists at that time to declare Mars inhospitable to life. NASA's Spirit rover, now operating closer to the equator, has also uncovered the salt.

Despite the thumbs-down verdict rendered on Mars by the Viking missions, planetary scientists have speculated in recent years that some locations might have the conditions necessary for rudimentary life-forms such as bacteria to get a start. All of these scenarios involve water, which on Earth is not only nourishment but a prime medium for life.


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