UD prof affirms Mars was much like Earth

True color image of the planet Mars
Photo courtesy of NASA

3:06 p.m., Oct. 21, 2005--Norman Ness, professor at UD’s Bartol Research Institute, and a team of NASA scientists have discovered additional evidence that Mars once underwent plate tectonics, slow movement of the planet’s crust, like the present-day Earth. A new map of the distant planet’s magnetic field made by the Mars Global Surveyor spacecraft reveals a world whose history was shaped by great crustal plates being pulled apart and smashed together.

Scientists first found evidence of plate tectonics on Mars in 1999. Those initial observations, also done with the Mars Global Surveyor’s magnetometer, covered only one region in the Southern Hemisphere. The data was taken from differing heights above the crust while the spacecraft performed an aerobraking maneuver.

The high-resolution magnetic field map, the first of its kind, covers the entire surface of Mars. The new map is based on four years of data taken in a constant orbit. Each region on the surface has been sampled many times. The more measurements we obtain, the more accuracy and spatial resolution, we achieve," Jack Connerney of NASA’s Goddard Space Flight Center in Greenbelt, Md., said.

“This map lends support to and expands on the 1999 results,” Ness, who retired from UD in June, said. “Where the earlier data showed a ‘striping’ of the magnetic field in one region, the new map finds striping elsewhere. More importantly, the new map shows evidence of features, transform faults, that are a ‘telltale’ of plate tectonics on Earth.”

Each stripe represents a magnetic field pointed in one direction--positive or negative--and the alternating stripes indicate a "flipping" of the direction of the magnetic field from one stripe to another. Scientists have seen similar stripes in the crustal magnetic field on Earth.

Stripes form whenever two plates are being pushed apart by molten rock coming up from the mantle, such as along the Mid-Atlantic Ridge. As the plate spreads and cools, it becomes magnetized in the direction of the Earth’s strong global field. Since that field changes direction a few times every million years, on average, a flow that cools in one period will be magnetized in a different direction than a later flow.

As the new crust is pushed out and away from the ridge, stripes of alternating magnetic fields aligned with the ridge axis then develop. Transform faults, identified by “shifts” in the magnetic pattern, occur only in association with spreading centers.

To see this characteristic magnetic imprint on Mars indicates that it, too, had regions where new crust came up from the mantle and spread out across the surface. When new crust comes up, old crust plunges back down--the exact mechanism for plate tectonics.

Norman Ness, who came to UD in 1987 after a long and distinguished career at NASA’s Goddard Space Flight Center, holds a model of the Voyager 1 space craft, which is now more than 8.7 billion miles from the sun, at the outer reaches of the solar system. Ness is one of two principal investigators who have remained with the Voyager project since its inception in 1971 and launch six years later.

Connerney said plate tectonics provides a unifying framework to explain several Martian features. First, there is the magnetic pattern itself. Second, the Tharsis volcanoes lie along a straight line. These formations could have formed from the motion of a crustal plate over a fixed “hotspot” in the mantle below, just as the Hawaiian islands on Earth are thought to have formed. Third, the Valles Marineris, a large canyon six times as long as the Grand Canyon and eight times as deep, looks just like a rift formed on Earth by a plate being pulled apart. Even more, it is oriented just as one would expect from plate motions implied by the magnetic map.

The results were published in a recent edition of the Proceedings of the National Academy of Science.

Other scientists working on the project included G. Kletetschka of the Catholic University of America, Washington, D.C., and NASA Goddard; D.L. Mitchell and R.P. Lin of the University of California-Berkeley; and H. Reme of the Centre d’Etude Spatiale des Rayonnements in France. Dr. Mario Acuña, Principal Investigator for the Mars Global Surveyor magnetic filed investigation, leads the international team that built and operates the Mars Global Surveyor magnetometers. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington.

Ness, who holds a doctorate from the Massachusetts Institute of Technology, was a research scientist and administrator at NASA’s Goddard Space Flight Center from 1960-86. He succeeded Martin A. Pomerantz as the director of the Bartol Research Institute in 1987 after a long and distinguished career at NASA’s Goddard Space Flight Center.

In 1991, the Bartol Research Institute became the lead institution in the NASA-funded Delaware Space Grant Consortium with Ness as director.

For more information on the results, visit [www.nasa.gov/vision/universe/solarsystem/mgs_plates.html].

Article by Martin Mbugua
Photo by Duane Perry

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