080610 clumpy martian soil

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Clumpy Martian soil challenges Phoenix instruments
BY DR EMILY BALDWIN
ASTRONOMY NOW
Posted: June 10, 2008

Phoenix engineers are testing a revised method for delivering soil samples to laboratory instruments onboard the lander now that researchers appreciate just how clumpy the soil is at the landing site.

"We're a little surprised at how much this material is clumping together when we dig into it," says Doug Ming a Phoenix science team member from NASA's Johnson Space Centre, Houston.

The contents of the robotic arm's scoop shows that the Martian soil is rather clumpy. The scoop is about 9 centimetres wide. Image: NASA/JPL-Caltech/University of Arizona/Max Planck Institute.

The physical properties of the soil are proving to be a challenge for getting a sample to pass through a screen over a delivery hatch into the Thermal and Evolved Gas Analyser (TEGA), which is designed to bake and sniff out samples to identify key ingredients. Images returned from the lander over the weekend showed that the robotic arm had delivered the dirt to the opening of the mini laboratory, and that the analyser had vibrated the screen for 20 minutes to try and filter the material out, but the sensor inside the instrument did not detect enough soil passing into the oven to be able to perform any experiments.

"We are going to try vibrating it one more time, and if that doesn't work, it is likely we will use our new, revised delivery method on another thermal analyser cell," says William Boynton of the University of Arizona, lead scientist for the instrument.

A sample of soil rests on a screen over the opening to one of eight ovens of the TEGA instrument. Image: NASA/JPL-Caltech/University of Arizona/Max Planck Institute .

The arm delivered the first sample to TEGA on Friday by turning the scoop over to release its contents. The revised delivery method will hold the scoop at an angle above the delivery target and sprinkle out a small amount of the sample by vibrating the scoop.

Phoenix used its robotic arm on Sunday to collect a soil sample for the spacecraft's Optical Microscope. Today's plans include a practice of the sprinkle technique, using a small amount of soil from the sample collected Sunday. If that goes well, the Phoenix team plans to sprinkle material from the same scoopful onto the microscope later this week.