PAIR OF TRENCHES left in the Martian soil by Phoenix Mars Lander's robotic arm. Soil from the right trench, nicknamed "Baby Bear," was delivered to Phoenix's instrument deck on June 6 but proved too crusty to pass through a fine screen for analysis in a narrow oven. The trench on the left, known as "Dodo," was dug as a test. Each one measures about three inches (nine centimeters) wide. NASA researchers said the excavated soil held its shape so well that Baby Bear and Dodo bear detailed imprints from Phoenix's shovel, down to the screw heads. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University
The case of the uncooperative soil is closed—for the moment, at least. NASA scientists announced yesterday that the Phoenix Mars Lander had succeeded in getting a stubborn pile of dirt to fall through a metal sieve into the first of eight ovens designed to analyze the soil's chemical composition.
Mission controllers had tried half a dozen times since the soil was scooped up and dumped onto the instrument deck last Friday to dislodge the sample by vibrating the metal screen above oven number four. On Monday they even tested a backup procedure—canting the shovel at the end of the probe's robotic arm and shaking it to dribble soil a bit at a time [see video below].
But when a seventh and final round of screen-shaking Tuesday night stopped abruptly, researchers found that the dirt had finally passed through the screen into the narrow confines of the oven, no wider than a pencil lead. "The dirt finally did start to flow and we finally got a full oven," William Boynton of the University of Arizona Lunar and Planetary Laboratory, lead scientist for Phoenix's Thermal and Evolved-Gas Analyzer (TEGA), said during a press conference yesterday.
NASA doesn't have a lot of room for error: The probe has only three months to do its job of analyzing Martian soil and ice before a long, sunless arctic winter blankets it in carbon dioxide ice, most likely putting it out of commission permanently.
Boynton said he hoped the oven door could be closed some time over the next few days to begin the soil analysis, which takes four days of heating and another day to flush Phoenix's mass spectrometer—a device that sorts chemicals by weight and electrical charge. He said that preliminary results should be in hand by the end of the five-day process, but "it's likely to be several weeks after that before we have definitive scientific numbers."
The sprinkle method, however, didn't go to waste. Images received early Thursday confirmed that Phoenix succeeded in shaking a scoopful of soil onto the sample wheel of the spacecraft's robotic microscope station.
NASA/JPL-Caltech/University of Arizona/Texas A&M University