In a news-filled week where the attention went to the Super Tuesday primaries, Iraq suicide bombings, the death of Marge Schott and even the phase-out of super-size fries, it may be understandable that the week's top science story has been overlooked.

But it's well worth noting a stunning discovery - proof that Mars once had a wet climate, with lakes or even oceans.

One of the two Mars robot rovers, Opportunity, has found clear chemical and geological evidence that rocks at its landing site "were once soaked with liquid water," NASA scientists announced Tuesday.

Opportunity, they said, may be sitting in the bed of what once was a body of water the size of one of the Great Lakes. The finding will advance our understanding not only of Mars, but of the processes behind our own planet's development.

The rover uncovered an "astounding amount" of salts after drilling into an outcropping of bedrock that shows sedimentary layering. Not only that, the salts were deposited in a pattern that matches what happens when saltwater pools dry up on Earth.

This puts scientists a bit closer to answering the Big Question: Is there or was there life on Mars? It seems more possible now that standing liquid water may have existed long enough on the surface to aid in life's development.

"The ground would have been suitable for life," science team member Steve Squyres of Cornell University said. "We believe that that place on Mars for some period of time was a habitable environment."

Anything more would be speculation - at least until NASA devises a mission, possibly to the same region at the end of the decade, that can collect soil samples and bring them back to Earth for analysis.

Others may be more certain. British bookies on Wednesday stopped taking bets on the possibility of finding evidence of life on Mars because, they said, it now is too likely we will find it. (You can still bet on whether there are living organisms on Mars now; odds are 500 to 1.)

But the big news is that the rovers fulfilled their mission to find evidence of water on Mars. This is exciting stuff, and it gives us added reason to keep exploring and discovering.