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Friday April 13, 2001

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Mars shores may be 'ridges'

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UA planetary science graduate Paul Withers describes the unique elevations of the surface of Mars beside the Kuiper Space Sciences building yesterday. Withers has recently gained media attention because of his theories that certain tectonic ridges on the surface of Mars were possibly not - in opposition to former theories - created by oceans.

By Jeremy Duda

Arizona Daily Wildcat

What were thought to be shorelines of ancient oceans on Mars may actually be tectonic ridges, scientists say.

The hypothesis that the large area of smooth, flat land in Mars' central plains was created by oceans was first proposed in an article published in 1999 in Science magazine, a weekly publication put out by the American Academy of Sciences.

More recent information has led Paul Withers, a UA graduate student who is working on his doctorate in planetary sciences, to believe that these "wrinkle ridges" may not have been formed by oceans at all.

"We were looking at some proposed shorelines and determined they looked more like tectonic ridges," he said. Withers worked at the NASA Goddard Space Flight Center in Washington D.C. last summer in a 10-week research fellowship program.

The topographical features in question were determined not to be shorelines due to inconsistencies with the shoreline formation process. The flat terraces were thought to indicate an ocean, but they are on the oceanward side of the alleged shoreline.

These ridges, said Withers, were most likely caused by major tectonic stress, which resulted in the formation of the volcanoes that dot the surface of Mars, some up to 10 miles high.

Ridges, which cover about one-fourth of the planet's surface, could be formed by volcanic activity or by the cooling of the planet as a whole, which could shrink or compress the surface, said Greg Neumann, a research scientist at the Goddard Center and the Massachusetts Institute of Technology. Neumann and Withers worked together on the project during the summer.

"There certainly was more tectonic activity than people previously thought," he said.

Images of the planet are received by NASA via the Mars Orbiter Laser Altimeter (MOLA), a high-resolution instrument used to make topographical maps.

MOLA creates images by sending pulses of light to the planet and determines the distance to the surface by measuring the time it takes for the pulses to reflect back to the spacecraft.

The points representing the height of different points on the surface, of which there are about 512 million, can be put together to make a topographical map. The image can be further enhanced with shading or by illuminating parts of it.

"It's like an x-ray image of the planet," Neumann said.

Withers emphasized that the tectonic activity theory is just a theory.

"I really don't have much of a clue why the surface is so flat and smooth. I think it's one of the most interesting questions in Martian geology."

"Nobody really knows what a 4 billion-year-old shoreline looks like, so that's a problem," Neumann said.