Confirming the watering hole
While the data behind the animated journey through time involves geology, it's the hypothesized hydrological implications that are the most interesting to anyone looking for water on Mars.
James Dohm and his colleagues have been investigating the Tharsis complex for years, resulting in their hypothesis of a basin and aquifer system. But until last year they had no hard evidence that there was actually any water there. Then at a conference in July 2000, Dohm heard a talk by Barlow, the University of Central Florida researcher, who was discussing her study of impact craters on Mars.
Around the craters, caused by asteroids and comets, Barlow and some colleagues had found a pattern of ejected material that looked like it was created not by solid rock, but by some sort of fluid.
"It's like if you took a rock and threw it in a mud puddle," she said.
Barlow's study involved a search for craters with the distinct pattern around them. And she found a bunch concentrated near the southern part of the Tharsis complex. Most were roughly 3 kilometers (about 1.8 miles ) in diameter and the ejected material had been excavated from about 110 meters deep. Logic dictated that there must have been water at that depth -- the water that created the fluid-like ejecta patterns.
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| SCIENCE TUESDAY | |
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| MARS TODAY: Still frame from the animation shows exaggerated Martian topography. The central Tharsis basin, which may still harbor an aquifer, has risen and possibly forced water outward.
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| AFTER SOME UPLIFT: Sometime more recently than 3.5 billion years ago, the great Valles Marineres begin to show. The central Tharsis basin, called Thaumasia Plateau, rises.
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| ANCIENT MARS: Tharsis region before most of the uplift occurred. Only a handful of mountains and rises surround the Tharsis basin, which may have held vast amounts of water.
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| MARS GLOBE: Shows the awesome size of Valles Marineris today. Olympus Mons is out of view around the left edge.
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|  | TODAY'S DISCUSSION | | |
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, a significant finding by itself.
But Barlow had also presented just what James Dohm needed: actual evidence of water in the same place he figured there had been a mechanism that might have driven water to or near the surface. The same water that then presumably flowed outward and helped carve the giant channels seen today.
Making an animation of the geology that pushed this water around has allowed the researchers to glean clues about how other less studied parts of the Tharsis region might have evolved.
Places to hide
If the geology of the Tharsis basin is as the team expects, water in the remaining aquifer has lots of places to hide.
"The rocks that compose the aquifer have many holes which can hold water, and many fractures which allow its movement," said Justin Ferris, the University of Arizona team member who is a hydrologist. Much of the aquifer is made of lava rock, believed to be porous. Ferris said regions of sandstone and limestone may be present in the aquifer, too.
"These are great aquifer materials," Ferris said. "So we have good reason to believe the aquifer can hold a lot of water."
Furthermore, Ferris thinks the aquifer has a network of natural underground "pipes" that can transport water easily from one place to another. The passageways are created when the brittle lava rock is fractured, caused either by the rising of the Tharsis region or when space rocks smack into the surface.
"These fractures act like a highway system for the water, allowing it to move easily within the aquifer system," Ferris said.
While the mounting evidence for water on Mars is tantalizing, particularly when its possible effects are animated, one truth runs through it: No one has seen anything definitively wet on or in the Red Planet. Which means that a tremendous discovery, if it is there, still awaits.
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