Citizen Staff Writer

ALAN FISCHER

afischer@tucsoncitizen.com

The Phoenix Mars Lander could begin analyzing soil samples as early as Tuesday, mission scientists announced.

A balky scientific instrument called the Thermal and Evolved-Gas Analyzer has been fixed, said Peter Smith, the mission’s principal investigator.

While many yearn for immediate results, it will take about four days for TEGA to analyze samples delivered by the Lander’s robotic arm, Smith said.

TEGA, which is designed to heat and study soil and ice samples scooped from the planet’s northern arctic region, was found to have an intermittent short-circuit in one of its two ion-producing filaments last week, Smith said.

Researchers switched the shorted primary filament with a backup, Smith said, and test results received Sunday night were successful.

“We got the same sensitivity using the secondary filament as the primary,” Smith said. “TEGA is prepared to go ahead and do the science we anticipated.”

The Lander’s 8-foot robotic arm could deliver a sample for analysis to TEGA as early as Tuesday, said Ray Arvidson, lead scientist for the arm.

“We want to make sure we are doing this right,” Arvidson said. “We want to go carefully and make sure the instruments are ready.”

The arm Sunday successfully dug a trench in the Martian soil and dumped the material to the left of the hole from a height of about 20 inches, he said.

Images of material inside the arm’s scoop show small amounts of white materials that researchers believe are either ice or a salty substance, said Arvidson, who is with Washington University in St. Louis.

The white material’s composition will be determined by TEGA analysis, he said.

Researchers are analyzing Martian surface images to select the initial three contiguous digging sites, he said.

Materials scooped from those sites will be delivered to and analyzed by TEGA and the optical microscope and chemistry labs of the Microscopy, Electrochemistry and Conductivity Analyzer, he said.

Providing all three instruments with samples from the same area and depth will allow scientists to compare results among the devices, he said.

Each sample analyzed by TEGA is tiny – about one-fifth of a teaspoon – said William Boynton, the lead TEGA scientist.

TEGA analysis results won’t be quick, Smith said.

The first phase of analysis will see TEGA heat the samples to about 100 degrees Fahrenheit to drive out some water vapor, Smith said.

The second phase will use a higher temperature of 347 degrees Fahrenheit to drive out more vapors. The third phase will see the instrument heat the sample to 1,800 degrees Fahrenheit to determine the actual mineral structures present in the sample.

“That’s enough to drive gases out of the most recalcitrant soils,” Smith said.

The baked sample – now rendered inert by heat – will again be heated to 1,800 degrees Fahrenheit to give the instrument a baseline measurement, Smith said.

The $420 million mission led by the University of Arizona is seeking evidence of water or elements of life on Mars.

The primary mission is slated to last 90 Martian sols – equal to 92 Earth days – or until a lack of sunlight for the craft’s solar panels and the cold Martian winter brings the project to an energy-starved end.

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