Friday April 30 3:09 AM ET

Mars' Magnetic 'Zebra Stripes' May Suggest Life

By Deborah Zabarenko

WASHINGTON (Reuters) - Magnetic ``zebra stripes'' on Mars suggest that tectonic plates once slammed into each other much as they do on Earth, fueling speculation about ancient life on the Red Planet, scientists reported Thursday.

Plate tectonics -- which is the way big sections of a planet's surface slide around over billions of years -- was thought to be a process that only happened on Earth and that required water, a basic precondition for life. If it happened on Mars too, that would add new ammunition for those who believe life existed there at one time.

``If it were possible to say that early Mars did in fact have plate tectonics, that would be another argument that would lead you toward expectation of life on Mars, because it would be more Earth-like,'' said John Connerney, one of the authors of a report on the subject in this week's edition of the journal Science.

Mars and Earth are like fraternal twins created 4.5 billion years ago, Connerney said in a telephone interview. Bigger twin Earth is still driven by its fiery heart to push its continents apart and smash them together, while Mars is cold with only magnetic indications that this once took place.

Steve Maran, assistant director of space sciences at NASA's Goddard Space Flight Center, where Connerney is based, called the report ``mind-blowing.''

``(Connerney's report means) The early Mars was like an early Earth and something made that all go away,'' Maran said by telephone. ``It's gone from a live planet to a dead planet and it increases our interest in getting sample rocks back and looking for the possibility of early microbial life on Mars.''

Not all are convinced. In an accompanying article, paleomagnetist Ronald Merill of the University of Washington, Seattle, was quoted as saying, ``If plate tectonics was operating on Mars, it worked differently or it was recorded differently by the rocks.''

Connerney's research was based on data gathered by the Mars Global Surveyor, an unmanned craft launched by the National Aeronautics and Space Administration to repeatedly orbit the planet at low altitude, low enough to see patches of magnetized rock on the surface.

At first, the magnetized patches seemed random, but as the spacecraft gathered more information, a pattern of ``zebra stripes'' of positive and negative charges emerged -- very similar to what scientists found on the sea floor of Earth, but on a much larger scale.

On Earth, scientists believe the stripes were created when tectonic plates spread apart, letting molten metal called magma bubble up, creating undersea ridges. On either side of the ridges, the iron in the magma cooled and magnetized, solidifying in the direction of the prevailing magnetic field, which changes every 10,000 years or so.

On Mars, the stripes seem to be more strongly magnetized and much larger, but Connerney theorized they were formed by plate tectonics, the same process that on Earth accounts for earthquakes, volcanoes and some mountain ranges.

Earth's oceans are essential to the process, lubricating the plates and helping them slip more easily. But this does not necessarily mean there were ever oceans on Mars -- though Connerney believes some water was necessary, possibly enough to support some kind of life.

``It would be surprising if water weren't there, in apparent river beds and large canyons,'' Connerney said. ``The real mystery today has been, what happened to the water?''