Sunday, June 8, 2008

Soil covers the screens leading to Phoenix’s TEGA. Image: NASA/JPL.

NASA has stated that the Mars Phoenix lander is having trouble analyzing soil samples that its robotic arm is collecting. According to NASA, the soil appears to be too clodded to pass through screens on the way to Phoenix’s Thermal and Evolved-Gas Analyzer (TEGA).

Images taken by the lander’s camera shows that the robotic arm has dumped a large portion of soil over the TEGA, but it failed to register any soil which might have passed through the screens leading into the analyzer. The screen is designed to let through particles up to one-millimeter (0.04 inch) across while keeping out larger particles, in order to prevent clogging a funnel pathway to a tiny oven inside. An infrared beam crossing the pathway checks whether particles are entering the instrument and breaking the beam. It is now believed that the particles are either too large to pass through the screen, or the soil is too clumpy.

“I think it’s the cloddiness of the soil and not having enough fine granular material. In the future, we may prepare the soil by pushing down on the surface with the arm before scooping up the material to break it up, then sprinkle a smaller amount over the door,” said Ray Arvidson of Washington University located in St. Louis, Missouri. Arvidson is the Phoenix team’s science lead researcher for Saturday and digging czar for Phoenix’s mission.

NASA also plans to use a shaker inside the TEGA to shake any material or samples longer than previously planned in an attempt to break up the larger particles and clumps. Phoenix already utilized this method on Friday June 6, shaking the soil for five minutes before dumping it onto the screen. NASA plans to tell Phoenix to shake the material a little longer in order for the soil to be tested.

While scientists ponder ways to fix the issue, TEGA will not be analyzing any samples. Instead Phoenix is expected to have completed tasks today such as horizontally extending a trench where the lander dug two practice scoops earlier this week, and taking additional images of a small pile of soil that was scooped up and dropped onto the surface during the second of those practice digs.

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