WEST GLACIER - When the Martians landed in Glacier National Park, with tiny lenses magnifying their eyeballs, they could not see the mountains for the rocks.

"Take me," they said, "to your stromatolites."

And so the University of Montana's Don Winston did just that, and the Martians pressed their noses hard to the gritty limestone cliffs, peering through those powerful lenses to an ancient time when their planet and ours were, perhaps, not so very different.

"We just don't know," said Marsman and scientist Alfred McEwen.

His words were mumbled, what with his lips being so close to that rock wall, but he pulled away, finally, and turned to a stone-studded sea of Glacier Park peaks.

"Planetary geology is always very humbling," he said. "It's very hard to reconstruct an ancient time. There are things here, though" - and he gestured toward the cliff he'd been inspecting so closely - "that do appear to be direct analogs with Mars. There are a lot of questions about Mars, but it's a long ways away; so understanding the geologic processes here is very important."

Glacier Park, of course, is no analog for Mars; it has goats, after all. But it does provide a practice ground of sorts, a place where scientists can presume a certain amount of familiarity when learning how to read rock, and how to infer what was by what is.

That, in fact, is exactly why 30-some self-described Martians - members of the team that operates the camera on the Mars Reconnaissance Orbiter -landed here for their week of summer work.

McEwen is one of a select few who will decide where to land NASA's next rover to Mars, a $2 billion project scheduled to lift off in 2011. He's particularly suited for the job, because he's also the lead scientist in charge of the very powerful camera on board the orbiter, which has been circling the red planet since 2006.

His camera's called HiRISE - short for High Resolution Imaging Science Experiment - and it can see Martian features as small as a meter across.

Among HiRISE finds: Mars was likely quite wet at one time. Mars has avalanches. Mars is home to sedimentary rock, which looks a whole lot like the rock in Glacier National Park.

That last was particularly interesting, because for years scientists had thought Mars was made pretty much of volcanic rock - basalts and high-temperature igneous geology, scoured by erosive winds.

"But there's been an amazing explosion of Mars information in the past decade," said Matt Golombek, lead scientist on the 1997 Pathfinder mission. "We're in the renaissance of Mars exploration and understanding."

Like understanding that Mars isn't entirely volcanic.

Several years ago, a European orbiter revealed what looked like sedimentary rock layers. Twin rovers Opportunity and Spirit later confirmed that find, and then HiRISE brought it into sharper focus, sending home 80 terrabits of imagery in just two years.

"We saw very regular and repeating sedimentary layers, some of them four meters thick," McEwen said. "What causes such apparent periodicity? What is the regular process through time? Fortunately, we have the same cycles right here, on Earth, where we can study it hands-on."

Since the discovery of a sedimentary Mars, hints of water and clay and hydrated sulfate minerals have sparked much discussion as to how those sedimentary layers were deposited. Were they laid down in water? And if so, did the watery world persist long enough for primitive life to take hold?

Up in Glacier Park, the Martians' tour guide through time (if not space) has been eyeing age-old stone for decades, looking back a billion and a half years into Precambrian-age Belt series rock. Winston, UM professor emeritus of geology, has mapped a vast basin - an ancient proterozoic seabed - into which sediments layered up to 18 kilometers thick.

These are rocks from time's dusty attic, before animals or land plants - remarkably preserved by comparison with other old-rock sites on Earth - "and the landscapes," Winston said, "were much different from today."

His job is to re-create those landscapes, making inferences about geologic processes based upon the leftover sedimentary structures. In that, his task is not so different from that of the Martians.

"The same rules of physics and chemistry apply on Mars as on Earth, and presumably the same laws of biology, as well," said John Grotzinger. "The modern is the key to the past."

Grotzinger is lead project scientist on that 2011 rover mission, and his face was pressed tight to a Glacier Park cliff, too. He's the kind of Martian who can talk about Aeolian cross-bedding and subaqueous dunes while eating huckleberries, and he was inspecting, up close and with a hand lens, an ancient stromatolite curling through Winston's Belt rock.

Grotzinger calls his rover the Mars Science Laboratory, or MSL, but the world knows it as "Curiosity," which was the name offered by a Clara Ma, a 12-year-old from Kansas.

Curiosity, Grotzinger said, will be "as big as a Mini Cooper, and it literally weighs a ton."

By comparison, the Pathfinder rover - which went to work in 1997 - was the size of a shoebox. Spirit and Opportunity, both now in their fifth year roving the fourth rock from the Sun, are about as big as a pair of golf carts.

The new robotic machine will carry lots of high-tech tools, including a full-color hand lens of its own, the better to view Martian stone at 40 microns. Curiosity also has a complete array of powerful cameras - including some whose resolution exceeds human acuity - and a 6-foot arm equipped with sort of a high-tech Swiss Army knife - drills, movie cameras, jackhammers. There's a mass spectrometer, and a gas chromatograph, and tools to analyze isotopic composition.

In other words, it's a remote field geologist, complete with on-site laboratory, on the hunt for life's signature. It can find minerals that formed in the presence of water, and it can sniff out the chemical building blocks of life.

Like Winston, it can read rock.

And wouldn't it be cool, Grotzinger said, if it found a stromatolite to read. Because in the hunt for life on Mars - and planetary habitability is what all these missions are about - a stromatolite would suggest much about the red planet's former potential.

Stromatolites are the leftovers of very early life, evidence of primitive blue-green algae set in stone.

Their 1.5 billion-year-old footprints - among the most ancient records of life on Earth - can be seen up and down Glacier Park's famed Going-to-the-Sun Road, and look a bit like fossilized cabbages.

Stromatolites remain top among the signs that can point to nascent life.

"If we look at Mars, and find geologic structures reminiscent of very early life on Earth, and then if we find a similar carbon signature, then maybe we have something to work with," said Tim Parker, a science team member on several Mars explorations. "Maybe we can begin to figure out Earth's life history."

There's a troubling gap, Parker said, between Earth's early life evidence and it's more recent fossil record, and he'd like to fill in that gap with knowledge.

"What did life here look like at that stage?" he wonders. "Maybe Mars has preserved some of that history."

Reporter Michael Jamison can be reached at (406) 862-0324 or at mjamison@missoulian.com.