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Mars' largest riverbeds formed by lava, not water

August 14, 2011 - Washington

The largest ancient riverbeds on Mars were created not by water, but by massive, fast-moving, low-viscosity lava flows that ravaged the planet's surface in a way we don't see on Earth, a US researcher says.

David Leverington, an associate professor in the Department of Geosciences at Texas Tech University, used recent high-resolution photographs and mineralogical data to help lay out his theory for why lava is a much more likely culprit for creating the largest class of the outflow channels and canyons, which can stretch up to 1,800 miles.

The Martian outflow channels superficially resemble channels on Earth that formed by floods from giant glacial lakes. However, unlike Earth's water-formed channels, Leverington said the large Martian canyons do not feature obvious river deposits and don't terminate in delta-like, sediment-laden mouths, such as at the end of the Mississippi River.

Instead, they fade into vast plains composed of volcanic basalt, he said.

"We see abundant evidence for past eruptions of lava at the heads of these large systems, for flows along these systems and for extraordinarily large volumes of lava at the mouths of these systems," he said. "These characteristics are very similar to what we see at volcanic channels on the moon and on Venus.

"There's really no known process for the rapid eruption of large amounts of water from aquifers to form channels that are thousands of miles long. We do have evidence of this happening through past volcanic processes on the moon and Venus," he added.

The study will be published in Geomorphology.


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