The soil at the landing site of NASA's Phoenix Mars Lander has proved to be a bit clumpier than researchers anticipated. Over the weekend, Phoenix scooped up a shovel-full of ruddy dirt using its 7.7-foot (2.4-meter) robotic arm to deposit into its Thermal and Evolved-Gas Analyzer, a suite of tiny, single-use ovens for baking soil and ice samples to study their chemistry. But instead of easily passing through a series of metal screens that cover the oven opening, which are designed to sift the smaller particles from the sample, the dirt sat there in a pile. On Sunday, mission controllers instructed Phoenix to turn on a mechanical screen shaker to loosen the soil. NASA said that results from the shaking should be reported today.