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Phoenix lander's robot arm grabs a scoop of Mars BY STEPHEN CLARK SPACEFLIGHT NOW Posted: June 2, 2008 The robotic arm on NASA's Phoenix lander dug several inches into the Martian tundra this weekend, scraping up bits of soil with what looks like small clumps of embedded ice, mission scientists said Monday.
"Today we can report our first interactions with the surface itself and pictures of the surface soils," said Peter Smith, Phoenix principal investigator from the University of Arizona. Scientists first used the arm to make an imprint on the surface to test the ground's ability to guide the 7.7-foot-long structure to specific points around the lander. The test formed a footprint-like marking in the dirt, inspiring managers to name the new landmark "Yeti." The arm was then ordered to dig a trench several inches deep to collect soil from the surface inside a small scoop. Phoenix downlinked several images showing unidentified white markings scattered within the rust-colored soil inside the arm's scoop. The white material is likely either ice or a salt similar to magnesium sulfate, officials said. "We're really carrying two ideas here," said Ray Arvidson of Washington University in St. Louis, co-investigator for the Phoenix robotic arm. "One is that we're seeing that (magnesium sulfate) material is cementing the soil and making it a little bit cohesive, or that we have actually exposed the top of the ice table and that we had a little bit of ice in the scoop before we dumped," Arvidson said. Mission planners are narrowing down a list of candidate sites for the next series of digs. Arvidson said the science team wants to collect three samples from an area near the location of Sunday's dig to drop inside three instruments on Phoenix for detailed analysis. "What we want to do is get surface samples from contiguous areas so we're looking at the same materials with the three different instruments," Arvidson said. Scientists should select a site for the next dig overnight, and officials hope to send commands for the arm to scoop up another soil sample sometime Tuesday or Wednesday. That sample will be put inside the Thermal and Evolved-Gas Analyzer, an instrument that includes eight tiny single-use high-temperature ovens and two sensors designed to determine the chemical make-up of the soil. Subsequent samples collected from the same region will be analyzed by the Microscopy, Electrochemistry and Conductivity Analyzer instrument's optical microscope and wet chemistry lab, an experiment that measures the characteristics of soil particles after water is added inside beakers. The sample put inside TEGA this week will spend at least four days going through a series of heating cycles inside one of the instrument's ovens, eventually reaching temperatures of about 1,800 degrees Fahrenheit. The first two cycles are designed to remove water and other volatile gases from the sample, so scientists may know whether ice is present early in the heating process. The final cycle will reveal the sample's mineral structure in detail, Smith said. TEGA was the subject of several days' worth of troubleshooting over the weekend after the Phoenix ground team noticed an apparent short circuit with a filament in the device's mass spectrometer. The filament provides a charge to soil particles coming from the instrument's oven. "If the filament that ionizes these materials is shorted, of course you get no charge at all and the instrument doesn't work," Smith said. Controllers switched a backup filament to primary mode, solving the problem and restoring the TEGA instrument to operational status. "We have the same sensitivity that we expected to have with the original filament that appeared shorted, so that's really good news for us," Smith said. Phoenix spent Monday removing protective covers from the TEGA instrument and collecting high-resolution stereo images of a light-colored area directly underneath the lander named "Holy Cow." Scientists say "Holy Cow" looks like it could be a slab of ice revealed after a top layer of dust was blown away by the probe's descent thrusters during its May 25 landing. "We want to go carefully here and make sure all the instruments are ready, but in terms of the robotic arm and the scoop, we're good to go as soon as we're cleared to do delivery," Arvidson said. The soil found by Phoenix is similar to material studied at the landing sites of the Spirit rover and the Viking probes three decades ago. Arvidson said the texture of the soil is comparable to garden soil. "I'm just struck by how crusty the material is in the scoop images, and finally the presence of some light-toned material, either ice or cemented soil. It remains to be seen exactly what the light-toned stuff is," Arvidson said.
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VIDEO:
FRIDAY'S BRIEFING REVEALS POSSIBLE ICE 