A remote-controlled spacecraft is expanding our knowledge of Mars, and NASA scientists are pumped about what a robotic arm dug up last week while rooting around in red Martian soil. Images beamed 170 million miles to Earth from the Phoenix lander confirm the presence of ice.

This puts us an essential step closer to answering the question behind three decades of Mars exploration and centuries of speculation: Could there have been life there? The new clue mean Mars might once have had liquid water, which is essential for life -- at least as it is known on Earth.

Though Mars is much too cold now to have liquid water on its surface, scientists believe that may not have always been true. Images from NASA missions in the 1970s showed channels and gullies, apparently carved by flowing liquid at some point in the planet's history. The current craft, which landed May 25 for a three-month mission, includes a digging tool at the end of a robotic arm that's nearly eight feet long.
Scientists now will do in-depth analysis to look for carbon, which forms the chemical backbone of proteins and fats. In addition to water, it is the major constituent of living cells and tissue.

NASA says: "It is with great pride and a lot of joy that I announce today that we have found proof that this hard, bright material is really water ice and not some other substance." -- Peter Smith, mission's principal investigator

Professor says: "We found what we were looking for. This tells us we have water ice within reach of the arm." -- Mark Lemmon of Texas A&M University, who works on the mission

Mars facts: Fourth planet from the sun in our solar system. About half the radius of Earth. Can be seen from Earth with the naked eye.