Meteorites that crashed into the Martian surface last year exposed buried ice to the digital eyes of NASA spacecraft.

Scientists have used those images to deduce that there is a lot more ice on Mars — and that it's closer to the equator — than previously thought. In fact, subterranean Martian ice should extend all the way down beyond 48 degrees of latitude, according to the model, which was published in Science Thursday.

That happens to be where the Viking Lander 2 was in operation from 1976 to 1980. As part of its science program, the Lander dug a trench about 6 inches deep. The new model predicts that if it had gone an extra 3.5 inches — a bit longer than a credit card — it would have hit ice.

It's difficult to project backwards in time what that discovery would have done to the Martian science program, but its impact could have been large.

"To find ice that far from the pole where Viking 2 was, it would have changed the way everyone looked at Mars for the next 20 years," said NASA Goddard archivist, David Williams, who curates the Viking project historical site. "It would have been a whole different model for Mars... If they'd dug down just a little more, they'd have this complete opposite view of Mars."

At the time, scientists didn't really know a lot about the Red Planet. Finding ice underground might not have been that surprising, but largely because the planetologists didn't have a lot of firm theories about water on Mars. They thought there was ice at the poles, Williams said, but not much more than that.

Unlike the Phoenix Lander, the Viking 2 Lander's trenching tool wasn't designed to search for or find ice. Its job was to deliver Martian soil to a series of tests.

As such, Viking 2 wouldn't have been able to do much with any hard ice that it found, said Steven Squyres, an astronomer at Cornell and lead investigator of the Mars Rover missions. Its arm just wasn't powerful enough. Squyers also noted that the Viking missions were a tremendous success, without a water ice find.

But the Viking 2 Lander's work did give the impression that water ice did not exist near the Martian surface in the mid-latitudes. We'll never know how NASA's "Follow the Water" missions to Mars might have changed if, for some reason, the Lander had been commanded to dig just a bit deeper and hit a hard, icy surface.

It goes to show that sometimes scientific discoveries can come down to a few inches and some luck, even on the surface of a planet hundreds of millions miles away.

See Also:

WiSci 2.0: Alexis Madrigal's Twitter, Google Reader feed, and green tech history research site; Wired Science on Twitter and Facebook.**