National Aeronautics and Space Administration scientists are eager to analyze the samples, since the solar-derived power Phoenix generates continues to decrease as late summer turns into fall on Mars' northern plains.

NASA said the spacecraft's robotic arm is also digging into the lower portion of the Phoenix worksite area. Its Surface Stereoscopic Imager is taking photos of the trenching so scientists can better map out the geology of the Red Planet's ice table.

"We're basically trying to understand the depth and extent of the ice table to tie together how geology and climate control its formation," said Phoenix mission scientist Diana Blaney of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Phoenix has operated nearly five months on Mars since landing May 25.

The mission includes contributions from the Canadian Space Agency, the University of Neuchatel in Switzerland, the universities of Copenhagen and Aarhus in Denmark, the Max Planck Institute in Germany and the Finnish Meteorological Institute.