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This artist's rendering shows Phoenix lander as Martian winter sets in. ((NASA/Associated Press))

Sharp new images received Saturday from the Phoenix lander largely convinced scientists that the spacecraft's thrusters had uncovered a large patch of ice just below the Martian surface, team members said.

That bodes well for the mission's main goal of digging for ice that can be tested for evidence of organic compounds that are the chemical building blocks of life.

Team members had said Friday that photos showing the ground beneath the lander suggested the vehicle was resting on splotches of ice. Washington University scientist Ray Arvidson said the spacecraft's thrusters may have blown away dirt covering the ice when the robot landed a week ago.

On Saturday, scientists said a more detailed image taken under the lander shows one of the craft's three legs sitting on coarse dirt and a large patch of what appears to be ice — possibly 90 centimetres in diameter — that apparently had been covered by a thin layer of dirt.

"We were worried that it may be 30-, 40-, 50-centimetres deep, which would be a lot of work. Now we are fairly certain that we can easily get down to the ice table," said Peter Smith, a University of Arizona scientist who is the chief project investigator.

The spacecraft is equipped with a backhoe-like robotic arm that will be used to dig into the ground and retrieve samples for testing in the lander's small laboratories. The lander was sent to a spot on Mars' northern regions in hopes of finding frozen water, but just how deep underground it would be found was unknown.