NASA's Mars Phoenix Lander has accomplished one of the primary goals of its mission. It's robotic arm has delivered a sample of water ice to an on-board instrument for analysis.

Scientists chose the landing site near the north pole on Mars because they expected to find water there, but as NPR's Joe Palca reports, proved it turns out to be remarkably difficult.

JOE PALCA: In the past two months, the Phoenix Lander has sample the Martian soil, measured the weather and snapped thousands of pictures of the Martian countryside. The scoop at the end of the robotic arm has exposed white stuff that looks like water ice and acts like water ice, but to prove it's water ice, mission managers wanted to scoop some of the stuff into the TEGA, an onboard instrument that would analyze it.

Phoenix Project Manager Barry Goldstein says they could get the white stuff into the scoop, but then there was a problem.

BARRY GOLDSTEIN: It's clumpy, very clumpy.

PALCA: So clumpy, it would stick to the bottom of the scoop.

GOLDSTEIN: No matter how hard we tried, we couldn't shake it free of the scoop and get it delivered into the TEGA.

PALCA: So mission managers changed tactics. They had the lander scoop up drier soil and deliver that to the TEGA. To their delight, even though the sample appeared dry, the TEGA instrument showed it contained water. Peter Smith is Phoenix' principal scientist.

PETER SMITH: Our excitement is not so much that ice is made of H2O, it's what we're going to learn about the impurities that are associated with this ice: salts, minerals and all of the things that are going to tell us about the history and the chance that this is a habitable zone on Mars.

PALCA: Meaning maybe there was once life here. Smith says that if Mars were once a warmer planet, maybe some of this ice near the north pole was once liquid, and there's plenty of ice near the Phoenix landing site. Smith says you only have to scrape away two inches of dirt to see it.

SMITH: If you had a broom, you could actually make a skating rink here. It's really amazing.

PALCA: I was going to think you should have send up a Zamboni machine.

SMITH: Well we should've, yes. Maybe the next mission, we'll think to do that.

PALCA: Actually, the next mission will send another Rover to Mars to Mars, no Zamboni. Joe Palca, NPR News Washington.

AMOS: And you can see a slideshow of Mars images at

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