Phoenix used its robotic arm during the mission's 15th Martian day since landing (June 9, 2008) to test a "sprinkle" method for delivering small samples of soil to instruments on the lander deck. This image from the lander's Surface Stereo Imager shows the amount of soil delivered to the upper end the cover of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) by the time the test was finished.
Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M
Scientists were finally able to deliver a soil sample to an instrument aboard NASA's Phoenix Mars Lander, after several frustrating days of failed attempts, mission controllers announced.
The welcome news came on Wednesday morning, when Phoenix beamed back the results of its activities from the previous day to scientists on Earth.
For the last several days, scientists had tried to dislodge the clumpy soil sitting on top of a screen that basically feeds samples into the ovens. The soil was stuck outside the instrument's entrance. The solution was to run a vibrator on the Thermal and Evolved-Gas Analyzer (TEGA), which is designed to heat up the soil samples to analyze their composition.
None of the dislodging attempts since the soil was first delivered on Saturday had been successful, but scientists ran the vibrator for a seventh (and likely final) time on Tuesday night "in the off chance we might get lucky," said TEGA co-investigator William Boynton of the University of Arizona.
"The dirt finally did start to flow and we actually got a full oven, so that problem is now behind us," Boynton added. "We're hopeful that some time in the next few days we'll close the oven and begin the analysis process."
When Boynton announced the unexpected result to the Phoenix team, "the group just went up into cheers," he said as he played the song "(Shake, Shake, Shake) Shake Your Booty."
TEGA's tiny ovens will heat the samples up to progressively higher temperatures. The first aim is to vaporize any ice that might be in the soil, which can be detected by the instrument mass spectrometer. At higher temperatures, other minerals may decompose into vapors as well, particularly any that formed in a wet environment.
"We're looking for past interactions with water," Boynton explained.
Just why the soil took such coaxing to get into TEGA is a mystery. The soil is unlike anything scientists expected to encounter, said Phoenix principal investigator Peter Smith, as it tends to clump together in little clods.
Scientists aren't sure what in the soil is causing this clumpy behavior ? it could be a particular mineral, or, some speculate, water ice (which is thought to form layers just underneath the surface). Part of the reason ice is proposed as causing the clumps is that the ice could have sublimed after spending several days out in the Martian sunshine, finally loosening the soil.
Scientists got the news about TEGA after Phoenix was sent its commands for its next day, so they will return to it in the coming days. Phoenix will spend its next day on the red planet delivering a sample to its optical microscope.
After the problems encountered with dumping the soil into TEGA, mission scientists have devised a new method of sample delivery called "sprinkling." They will have the lander's robotic arm tilt its scoop, pushing the soil sample to the front. They will then switch on the scoop's rasp to vibrate and loosen soil, causing some of it to fall out in the instrument.
"It's kind of a salt-shaker mode if you like," Smith said. "We've practiced this before and we know it's going to work well."
"Delivering the soil is something we're getting better at everyday," Smith added.
The first look at a soil sample through the microscope should come on Thursday. This close-up look at the soil should give scientists a better idea of just what is in the Martian regolith. Scientists back at the University of Arizona have been trying to mimic the sample in their lab, but "there's something missing in our mixtures here, and I'm quite anxious to find out what it is," Smith said.
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