Magnetic Stripes on Mars Discovered
By PAUL RECER
AP Science Writer

WASHINGTON (AP) _ The discovery of magnetic strips across the face of Mars suggests the barren planet once had geology like that of Earth, with a torrid interior spurting molten rock and massive plates drifting on the surface. Instruments aboard the Mars Global Surveyor have detected magnetic striations that closely resemble the magnetic signature of crustal spreading and continental drift on the Earth, researchers report in a study to be published Friday in the journal Science. This may mean the very young Mars resembled the very young Earth, but that Mars ran out of its internal energy sources and became a geologically dead planet early in its history, said Norman F. Ness of the University of Delaware and co-author of the study. ``The data suggests that Mars was once magnetic and was far more similar to Earth's global magnetic field than had previously assumed,'' Ness said. Evidence of this magnetic field is frozen in rocks that were molten when the magnetic field existed. When the rocks hardened they retained the original magnetism and that now has been detected and mapped by the spacecraft. ``At the present time there is no evidence of a global magnetic field on Mars,'' said Ness. ``That means the dynamo died and what is left is the memory of that dynamo, stored in the crustal rocks like a magnetic tape recording.'' The pattern of magnetic rock closely resembles the streaks that led scientists to discover on Earth that continents sit atop immense crustal plates that inch about the globe over millions of years. Scientists previously believed that continental drift occurred only on Earth because studies had shown the process did not take place on Venus, the solar system planet nearest Earth's size, said Ness. But the discovery of Martian magnetic striations suggests that Mars may also have had continent-sized plates that split apart on the surface of the planet and inched apart, pushed by the flow of magma bubbling up through crustal rifts. Ness said the energy that heated the rock apparently ran out within a few hundred million years and Mars became a geologically dead planet. The solar system, including the Earth and Mars, are thought to have formed 4 billion years ago to 4.5 billion years ago. Vicki L. Hansen, a Southern Methodist University geologist, said that the fate of Mars also awaits the Earth. She said that eventually Earth also will exhaust its internal energy and its molten core will cool. This will shut down the planet's magnetic field and allow radiation from the sun to strip away the Earth's atmosphere and water. ``What Mars went through at a very young age is what will occur on the Earth eventually,'' she said. Ness said that Mars died much more quickly than Earth because the red planet is smaller and had much less internal heat generated by friction and the decay of radioactive minerals.
TO BE CONTINUED...