NASA’s Mars detector (̽²âÆ÷), Opportunity, succeeded in finding signs that water once existed on the planet. Opportunity landed on Mars in January. Scientists now believe that the planet could once have supported life.

This discovery was chosen by Science, one of the world’s leading magazines, as the most important scientific achievement of 2004 last Friday.

“This little, wheeled, one-armed box went around another planet and has done something no human has ever managed,” according to Science. “It has discovered another place in the universe where life could once have existed.”

“Although we still can’t say that life could have existed in this environment, it is now certain that there was water on Mars,” said Steve Squyres, one of the scientists working on the Mars mission. The evidence comes from pictures and chemical readings taken by Opportunity. It includes marks on rocks like those caused by flowing water on Earth and salty chemicals like those found in dried-out sea-beds. Scientists said the new evidence proved beyond doubt that water has been existed on Mars. But it is still unknown whether the water on Mars was like an ocean or just ice.