At least not where previously thought

Sep 24, 2007 07:29 GMT  ·  By
Martian gullies show the same channels, terraces, and other features seen in water-carved regions on Earth
   Martian gullies show the same channels, terraces, and other features seen in water-carved regions on Earth

Just when everybody was so excited about recent theories of a former watery Mars, on the contrary, new images of this planet reveal a drier planet, contradicting the so-called geologic records of liquid water near the planet's surface.

"It has always been highly unlikely, because it would be hard to maintain liquid water [in the Martian environment]. Now it appears even less likely." said lead researcher Alfred McEwen at the University of Arizona in Tucson, whose study is based on high-resolution images from the Mars Reconnaissance Orbiter (MRO).

"The [new MRO data] will help to determinewhere to focus future exploration, where to send landers, and where to pursue the search for life on Mars," said McEwen.

In recent years, frozen water has been detected beneath the Martian surface and also in the frigid planet's polar ice caps, but no liquid water, essential for life on Earth. Martian gullies and ravines have suggested recent flows of liquid water, but MRO's new images reveal another story.

Martian Athabasca Valles is a web of channels and islands similar to Washington State's Channeled Scablands, created due to massive flood millennia ago. Athabasca Valles could have formed a few million years ago, but the new images show that the whole area is covered with a thin lava layer. If the AV is modeled by liquid water, this should have been present long before the lava flows occurred.

Some still stick to the idea of a wet Mars.

"The [researchers] are not saying that the valley was not originally carved by water, it's just that it was subsequently covered by lava. As the observable lava fill is not tied to water-related processes that carved the channels, the age of the channel formation is now uncertain," said Roger Phillips, a professor of earth and planetary sciences at Washington University in St. Louis.

The new research also attacks the hypothesis of the presence of an ancient Martian ocean located on the planet's northern lowlands. Previous images made the researchers believe the area is a sandy, sedimentary seabed, while the new images present large boulders that do not match the idea of the ancient ocean floor.

"The whole ocean hypothesis is extremely controversial in the first place. Explaining why the boulders would exist if the region was once an ocean would require a new and probably less-likely hypothesis," said Phillips.

The Martian gullies have bright deposits that some believed they were the result of recent flowing water, while the new images show they were the result of landslides and their bright color is not induced by the presence of water or ice.

"[The new data] doesn't prove that it wasn't water that created the deposits. But given the difficulties of explaining how liquid water could be on the Martian surface in the present climate, [the landslide theory] is a more conservative hypothesis." said McEwen.

But the new MRO data have also come with some possible proof for running water in the last millions of years on other locations of Mars. The 37-mi (60 km)-wide Mojave Crater presents runoff patterns similar to alluvial fans (made by flowing water) in Earth's deserts. The Martian fans could have been induced by heat from the collision that created the crater melted subsurface ice. Part of this ice flowed briefly as liquid water.

"They are basically saying that there is good evidence that there is ice in the crust even today and even at low latitudes. That, I think, is the most interesting result." said Phillips.