The one snag on the lander occurred when the protective sheath around the trench-digging robotic arm failed to unwrap all the way after touchdown and now covers the arm's elbow joint.

Deputy project scientist Deborah Bass, of NASA's Jet Propulsion Laboratory, said scientists still planned to start the process of unstowing the arm, but it could take an extra day to fully stretch the arm.

Since landing on Mars, Phoenix has delighted scientists with the first-ever peek of the planet's unexplored northern latitudes.

The terrain where Phoenix set its three legs is relatively flat with polygon-shaped patterns in the ground likely caused by the expansion and contraction of underground ice.

Phoenix is on a three-month mission to excavate the soil using its 8-foot-long (2.4-meter-long) robotic arm to reach the ice believed to be buried inches to a foot (up to 30 centimeters) deep.

The lander will study whether the landing site could have supported primitive life. Among the things it will look for is whether the ice melted in Mars' history and whether the soil samples contain traces of organic compounds, one of the building blocks of life.